‘ لغوتلا لادعمب اهتقلاعو رفحلا لاماعم drilling ...eng. wael rashad...

Faculty of Engineering

Drilling Parameters In Relation To

Penetration Rates, As a Tool to Predict

the Type of Rock

MSc. Thesis

Submitted by

Eng. Wael Rashad Elrawy Abdellah

Department of Mining and Metallurgy

Engineering

Faculty of Engineering – Assiut University

2007

كليـة الهندســة

‘ بمعدالت التوغل معامالت الحفر وعالقتها

نوع الصخر لتوقع كوسيلة

تيررسالة ماجس

مقدمة من

عبدالاله وائل رشاد الراوى المهندس/

التعدين والفلزاتهندسة قسم

جامعة أسيوط –كلية الهندسة

م 7002

Drilling Parameters In Relation To Penetration

Rates, As a Tool to Predict the Type of Rock

By

Wael Rashad Elrawy Abdellah

B.Sc., Mining and Metallurgy Engineering

Assiut University, 2003

A THESIS

Submitted in partial fulfillment of the

requirement for the degree

MASTER OF SCIENCE

Department of Mining and Metallurgy

ASSIUT UNIVERSITY

Assiut, Egypt

2007

Supervision Committee: Arbitration Board:

Prof. Dr. Mostafa M. El Biblawi Prof. Dr. Mahmoud F.El-Karamani

Prof. Dr. Mohamed A. Sayed Prof. Dr. Adel S.Abdel-Khalek

Dr. Mostafa T. Mohamed

Assiut University

Faculty of Engineering

Drilling Parameters in Relation to Penetration Rates, as a

Tool to Predict the Type of Rock

By

Wael Rashad Elrawy Abdellah

A thesis submitted to the Graduate Studies in partial fulfillment of the requirements for the

degree of

Master of Science

Department of Mining and Metallurgical Engineering

Assiut University

Assiut, Egypt

July 2007

Wael Abdellah 2007

All rights reserved.

i

ARABIC ABSTRACT

وعالقتها بمعدالت التوغل, كوسيلة لتوقع نوع الصخرمعامالت الحفر

فى هذا البحث تم استخدام ماكينة حفر دوار ذات بنطة مطعمة بالماس لعمل عينات أسطوانية فى ثالثة أنواع من

:فةالصخور والتى تمثل الصخور الرسوبية والمتحولة والنارية. وكانت على الترتيب الحجر الجيرى من خمسة مواقع مختل

المنيا , والرخام -ثالثة مواقع فى أسيوط هي الزرابى , منقباد , أسمنت أسيوط , العيسوية بسوهاج , وبنى خالد بسمالوط

األبيض واألسود من وادى المياه بالصحراء الشرقية , والجرانيت األحمر من أسوان, والجرانيت األسود من على طريق

مرسى علم.–إدفو

من البحث تمت دراسة تأثير كل من الحمل الواقع على البنطة وسرعة الدوران على معدل الحفر فى الجزء األول

والطاقة المستهلكة وعزم اللي أو التدوير وتم اختيار عدة أحمال وكذلك سرعات مختلفة باستخدام نوعين من البنط المطعمة

الذى يعطى أكبر معدل للحفر وأقل قيمة للطاقة بالماس إحداهما مستعملة واألخرى جديدة. واتضح أن الحمل المثالى

كجم لكل من حجر جيرى الزرابى 06كجم لحجر جيرى المنيا , 561كجم للحجر الجيرى "منقباد" , 06المستهلكة كان

056كجم. وكان فى الجرانيت األحمر 06والعيسوية وأسمنت أسيوط. وكان الحمل المثالى فى الرخام األبيض واألسود

5666كجم عند السرعة العالية ) 006لفة/دقيقة(, 066كجم عند السرعة البطيئة ) 086, وفى الجرانيت األسود كجم

لفة/دقيقة(.

وبعد حساب معدالت الحفر والطاقة المستهلكة عند األحمال والسرعات المختلفة تم توقيع العالقات بين الحمل على

لمستلهكة , وعزم اللي أو التدوير وكذلك معدل الحفر مع الطاقة المستهلكة. وتم البنطة وكل من معدل الحفر , الطاقة ا

استنتاج المعادالت الرياضية والتى تمثل هذه العالقات.

وفى الجزء الثانى من البحث أمكن التعرف على أنواع الصخور التى تم حفرها باستخدام معامل جديد هو عبارة عن

على الطاقة المستهلكة عند السرعات واألحمال المختلفة. ثم تم توقيع العالقات بين هذا قسمة مقاومة الصخر للضغط

لفة/دقيقة مع البنطة 5666لفة/دقيقة , 066المعامل الجديد ومعدالت الحفر لكل الصخور موضع الدراسة عند سرعتين هما

األحمال والسرعات العالية والمنخفضة لم يكن الجديدة وأحمال مختلفة. من هذه العالقات اتضح أنه عند استخدام مختلف

هناك فاصل واضح لألنوع المختلفة من الصخور وإنما كان هناك تداخل بينها ،وتم استبعاد األحمال الصغيرة و استخدام

لفة/دقيقة(أمكن التمييز بوضوح بين منطقتين فقط على الرسم واحدة تمثل 066األحمال الكبيرة مع السرعة المنخفضة )

الصخور الرسوبية واألخرى تمثل الصخور المتحولة والنارية معا.و عند استخدام نفس األحمال الكبيرة ولكن مع السرعات

لفة/دقيقة( أمكن التمييز بوضوح بين ثالثة مناطق على الرسم كل منها يختص بنوع بذاته من الصخور 5666العالية )

ة باإلضافة إلى بعض المعلومات عن الصخور من الفتات الناتج أثناء الحفر الثالثة. وعليه فإنه يمكن استخدام هذه الطريق

. للتعرف على أنواع الصخور التى يتم الحفر فيها

ii

English ABSTRACT

Three categories of rocks represent sedimentary, metamorphic and igneous rocks were

cored by a diamond core bit. Five types of limestone, three of them are from Assiut, namely:

Zaraby, Mankabad, and Assiut cement company quarry, and the fourth type of limestone is

from Issawyia, east Sohag, and fifth type is from Beni-Khalid, Samalout- Minia. Two types

of marble namely are: White and Black marble from Wadi-El-Miah, Idfu- Marsa Alam road,

Eastern Desert. Two types of granite namely, pink and Black granite from Aswan. Then the

most important physical and mechanical properties of the tested rocks were determined, such

as density, porosity, compressive strength, tensile strength, Shear strength and coefficient of

internal friction ().

A fixed laboratory-core drilling machine is used at two rotational speeds, 300 and

1000 rpm, at different ranges of weights on bit (WOB). Drilling parameters such as weight on

bit (WOB), rate of penetration (ROP), torque and drilling specific energy (SE) were

continuously monitored during the drilling operations. Two core bits were used in drilling

operations; one of them is new and the other is used. The effects of the drilling parameters on

the performance of the two bits were examined. Relationships between WOB and both ROP

and SE were also plotted.

Specific energy (SE) for drilling in all types of rocks under investigation at different

applied loads and rotary speeds have been determined and plotted against rate of penetration

(ROP) to show the variation in specific energy with the different rocks. A new dimensionless

index Uniaxial Compressive Strength divided by specific energy (UCS/SE) was calculated.

The rates of penetration (ROP) against (UCS/SE) for all tested rocks were plotted. The

interpretation of these relationships indicates that at lower thrust loads and higher rotary

speeds the three groups of rocks are lying into distinct zones. Whereas, at higher thrust loads

and higher rotary speeds; it is possible to obtain only two distinct areas for the three groups of

rocks, one for sedimentary only and the other for metamorphic and igneous together. From

these results together with other information obtained from analysis of drill cuttings it can be

possible to identify the rock category being drilled.

iii

DEDICATION

This work is dedicated to my parents: Rashad Elrawy and Irdina Hamdallah,

With all the warmth of a thankful son;

My wife: Lobna Sayed Mohamed;

My daughters: Mennatallah and Hebatallah;

And my siblings: Hazem, Manal, Mervat, Nashwa and Hala,

With all the joy of a lucky brother

iv

ACKNOWLEDGMENTS

First of all, my gratitude and thanks are for Allah, our creator and the most merciful. It

is the pleasure of the author to record his sincere thanks to Prof. Dr. Mostafa El-Beblawi,

Prof. Dr. Mohamed Sayed, and Dr. Mostafa Tantawy, Mining and Metallurgical

Engineering Department, Faculty of Engineering, University of Assiut, Egypt. I am truly

grateful for their support, generous portion of time, technical expertise, encouragement and

constructive criticism to transform what has been done. I wish to express my thanks to all

technicians and workers of the Department of Mining and Metallurgical Engineering at Assiut

University for their extensive help and cooperation. Finally, the author would like to thank

everyone who helped in one way or another in making this work come into light.

Eng. Wael Rashad Elrawy Abdellah

July, 2007

v

CONTRIBUTIONS OF AUTHORS

This thesis is prepared in accordance with the guidelines of the Graduate Studies office of

Assiut University. The following two manuscripts are published from this thesis:

1. Abdellah, W., Mohamed, M. T., Sayed M. ., and EL-Beblwi, M. M., Effect of Rotary

speed and Weight on bit on drilling rate and Specific Energy Using Different rocks,

The 10th

International Mining, Petroleum, and Metallurgical Engineering Conference

(MPM), Assiut University, Fac. of Eng. Min. and Metal. Eng. Dept., March 6-8, 2007.

2. Abdellah, W., Mohamed, M. T., Sayed M. ., and EL-Beblwi, M. M., Some drilling

parameters as a tool to differentiate between sedimentary, metamorphic, and igneous

rock, Journal of Engineering Science (JES), , Fac. of Eng. Assiut, Egypt, Vol.34, June,

2007.

vi

Contents ARABIC ABSTRACT ................................................................................................................ i

English ABSTRACT .................................................................................................................. ii

DEDICATION .......................................................................................................................... iii

ACKNOWLEDGMENTS ......................................................................................................... iv

CONTRIBUTIONS OF AUTHORS .......................................................................................... v

LIST OF TABLES .................................................................................................................... xi

CHAPTER 1 ............................................................................................................................. 1

1 Background ......................................................................................................................... 1

1.1 INTRODUCTION ....................................................................................................... 1

1.2 The specific objectives of this study............................................................................ 4

2 LITERATURE REVIEW ................................................................................................. 5

2.1 General ......................................................................................................................... 5

2.2 Historical Developments ............................................................................................. 6

2.3 Drilling methods ........................................................................................................ 10

2.3.1 Percussion drilling .............................................................................................. 10

2.3.2 Rotary drilling .................................................................................................... 16

2.3.3 Auger drilling ..................................................................................................... 19

2.3.4 Diamond drilling ................................................................................................ 20

2.3.5 Heavy rotary blast hole drilling .......................................................................... 21

2.3.6 Rotary- Percussive drilling ................................................................................. 22

2.4 Major factors influencing penetration rate ................................................................ 24

2.4.1 Weight on bit (WOB) and Rotary speed (RPM) ................................................ 25

2.4.2 Bit type and Condition ....................................................................................... 25

2.4.3 Rock properties .................................................................................................. 26

2.4.4 Fluid properties (Circulation) ............................................................................. 27

2.5 Automatic optimization of drilling techniques .......................................................... 28

vii

2.5.1 Drill productivity evaluation by monitoring ...................................................... 28

2.5.2 Rock characterization by monitoring ................................................................. 28

2.5.3 Measurement While Drilling (MWD) ................................................................ 29

2.5.4 Rotary and Percussive drilling rate prediction models ....................................... 30

2.6 Future perspective of drilling techniques .................................................................. 31

2.6.1 Safety and health ................................................................................................ 31

2.6.2 Productivity ........................................................................................................ 32

CHAPTER 3 ............................................................................................................................. 33

3 STEPS OF THE EXPERIMENTAL WORK AND PROCEDURES ............................... 33

3.1 Rock properties .......................................................................................................... 34

3.2 Drilling operations ..................................................................................................... 35

3.3 Experimental data of drilling tests ............................................................................. 39

CHAPTER 4 ............................................................................................................................. 47

4 RESULTS AND DISCUSSIONS ..................................................................................... 47

4.1 Effect of both weight on bit, rotary speed, and bit condition on rate of penetration . 47

4.2 Effect of both weight on bit, rotary speed and bit conditions on torque ................... 56

4.3 Effect of weight on bit, rotary speed, and bit condition on specific energy .............. 58

4.4 Relationships between rate of penetration (ROP) and specific energy (SE) for all

tested rocks ........................................................................................................................... 68

4.5 Identifying the rock type to be drilled using drilling parameters .............................. 74

4.5.1 I -Variation of specific energy with the rock types ............................................ 75

4.5.2 II- Relation between UCS/SE and ROP ............................................................. 78

CHAPTER 5 ............................................................................................................................. 82

5 CONCLUSIONS AND RECOMMENDATIONS ........................................................... 82

REFERENCES ......................................................................................................................... 85

viii

List of Figures

Figure ‎1.1: Location of map of the studied rocks ...................................................................... 3

Figure ‎2.1: different drilling methods [19] ............................................................................... 11

Figure ‎2.2: Cable tool drilling [30] ......................................................................................... 12

Figure ‎2.3: Down-the-Hole hammer schematic [31] ............................................................... 15

Figure ‎2.4: Diagram of Reverse circulation drilling system [42]. ........................................... 19

Figure ‎2.5: different types of drilling bits [19] ......................................................................... 26

Figure ‎2.6: schematic representation of the MWD system [59] .............................................. 29

Figure ‎3.1: Program of the experimental work ........................................................................ 33

Figure ‎3.2: Diamond core drilling machine ............................................................................. 37

Figure ‎3.3: Schematic representation of the drilling machine [11]. ......................................... 38

Figure ‎4.1: Relation between weight on bit (WOB) and rate of penetration (ROP) at 300 and

1000 rpm in Mankabad limestone, Assiut ................................................................................ 47

Figure ‎4.2: Relation between weight on bit and rate of penetration at 300 and 1000 rpm in

Beni Khalid- Samalout limestone, Minia ................................................................................. 48


Assiut limestone ....................................................................................................................... 48


Issawyia limestone, East Sohag ............................................................................................... 49


Zaraby limestone, Assiut .......................................................................................................... 49


Black marble, Wadi El-Miah ................................................................................................... 50


white marble, Wadi El-Miah .................................................................................................... 50


pink granite, Aswan .................................................................................................................. 51


Black granite, Aswan ............................................................................................................... 51

ix

Figure ‎4.10: Relation between weight on bit and torque at 300 rpm using new bit, For Zaraby

limestone (Assiut), white (Wadi El-Miah Eastern Desert), and pink granite (Aswan) ............ 57

Figure ‎4.11: Relation between weight on bit and torque at 300 rpm using used bit, For Zaraby

limestone (Assiut), white marble (Wadi El-Miah Eastern Desert), and pink granite (Aswan) 58

Figure ‎4.12: Relation between weight on bit and specific energy at 300 and 1000 rpm in

Mankabad limestone ................................................................................................................ 60

Figure ‎4.13: Relation between weight on bit and Specific energy at 300 and 1000 rpm in

Beni-Khalid, Samalout Limestone, Minia ................................................................................ 60


Assiut cement company quarry Limestone, Assiut .................................................................. 61


Issawyia Limestone, East Sohag .............................................................................................. 61


Zaraby Limestone, Assiut ........................................................................................................ 62


Black Marble, Wadi El-Miah, Eastern Desert .......................................................................... 63


White Marble, Wadi El-Miah, Eastern Desert ......................................................................... 63

Figure ‎4.19: Relation between weight on bit and Specific energy at 300 and 1000 rpm in pink

granite, Aswan .......................................................................................................................... 64


black granite, Aswan ................................................................................................................ 65

Figure ‎4.21: Relation between rate of penetration and Specific energy at 300 and 1000 rpm in

Mankabad Limestone, Assiut ................................................................................................... 69


Beni-Khalid, Samalout Limestone, Minia ................................................................................ 69


Assiut cement company quarry Limestone, Assiut .................................................................. 70


Issawyia Limestone, East Sohag .............................................................................................. 70


Zaraby Limestone, Assiut ........................................................................................................ 71

x


Black Marble, Wadi-El-Miah, Eastern Desert ......................................................................... 71


White Marble, Wadi-El-Miah, Eastern Desert ......................................................................... 72


Pink Granite, Aswan ................................................................................................................ 72


Black Granite, Aswan .............................................................................................................. 73

Figure ‎4.30: Relationship between average rate of penetration and specific energy for all

rocks at different loads and drilling speed of 1000 rpm ........................................................... 77

Figure ‎4.31: Relationship between average rate of penetration and specific energy for all

rocks at different loads and drilling speed of 300 rpm ............................................................. 77

Figure ‎4.32: Relationship between UCS/SE and Rate of penetration for all rocks at different

loads and rotary speed of 1000 rpm, new bit ........................................................................... 78

Figure ‎4.33: Relationship between UCS/SE and Rate of penetration for all rocks at different

loads and rotary speed of 300 rpm, new bit ............................................................................. 79

Figure ‎4.34: Relationship between UCS/SE and rate of penetration for all rocks at rotary

drilling of 300 rpm and loads of 45, 60, 75, 90, 120, 150, 180, 210, 300, 390 and 480 kg, new

bit .............................................................................................................................................. 81

Figure ‎4.35: Relationship between UCS/SE and rate of penetration for all rocks at rotary

drilling of 1000 rpm and loads of 45, 60, 75, 90, 120, 150, 180, 210, 300, 390 and 480 kg,

new bit ...................................................................................................................................... 81

xi

LIST OF TABLES

Table ‎2.1: Drilling methods for the various ground conditions [48]. ..................................... 23

Table ‎3.1: Physical and mechanical properties of the tested rocks .......................................... 35

Table ‎3.2: Data of the drilling parameters in Mankabad limestone, Assiut ............................. 39

Table ‎3.3: Data of the drilling parameters in Beni-Khalid- Samalout limestone, Minia ......... 39

Table ‎3.4: Data of the drilling parameters in Assiut cement company quarry limestone, Assiut

.................................................................................................................................................. 40

Table ‎3.5: Data of the drilling parameters in Issawyia limestone, east Sohag ......................... 40

Table ‎3.6: Data of the drilling parameters in Zaraby limestone, Assiut .................................. 41

Table ‎3.7: Data of the drilling parameters in Black marble, Wadi El-Miah, Eastern Desert ... 41

Table ‎3.8: Data of the drilling parameters in White marble, Wadi El-Miah, Eastern Desert .. 42

Table ‎3.9: Data of the drilling parameters in Pink granite, Aswan .......................................... 42

Table ‎3.10: Data of the drilling parameters in Black granite, Aswan ...................................... 43

Table ‎3.11: Specific energy and UCS/SE for limestone at 300, and 1000 rpm and different

loads, new bit ............................................................................................................................ 44

Table ‎3.12: Specific energy and UCS/SE for Marbles at 300, and 1000 rpm and different

loads, new bit ............................................................................................................................ 45

Table ‎3.13: Specific energy and UCS/SE for Granites at 300, and 1000 rpm and different

loads, new bit ............................................................................................................................ 45

Table ‎3.14: Average values of rate of penetration and specific energy at rotary speed 1000

rpm at different loads (WOB) ................................................................................................. 46

Table ‎3.15: Average values of rate of penetration and specific energy at rotary speed 300 .... 46

Table ‎4.1: Correlation equations of the relationship between rate of penetration and

the weight on bit for all tested rocks at 300 rpm ...................................................................... 52

Table ‎4.2: Correlation equations of the relationship between rate of penetration and the weight

on bit for all tested rocks at 1000 rpm ...................................................................................... 53

Table ‎4.3: Correlation equations of the relationship between Torque (T) and weight on bit

(WOB) at 300 rpm .................................................................................................................... 58

Table ‎4.4: Correlation equations of the relationships between (SE) and (WOB) for all tested

rocks at 300 rpm ....................................................................................................................... 66

xii


rocks at 1000 rpm ..................................................................................................................... 66

Table ‎4.6: Best drilling conditions for all tested rocks ............................................................ 67

Table ‎4.7: Predicted values of drilling rate (ROP, cm/min.) at the best weight on bit (WOB) as

an example for tested rocks ...................................................................................................... 67

Table ‎4.8: Predicted values of Specific energy (SE, Mpa) at the best weight on bit (WOB) as

an example for tested rocks ...................................................................................................... 68

Table ‎4.9: Correlation equations of the relationship between (SE) and (ROP) for tested rocks

at 300 rpm ................................................................................................................................. 73

Table ‎4.10: Correlation equations of the relationship between (SE) and (ROP) for tested

rocks at 1000 rpm ..................................................................................................................... 74

Table ‎5.1: The range of drilling parameters values related to the three types of rocks ........... 84

1

CHAPTER 1

1 Background

1.1 INTRODUCTION

Drilling is the essential operating step in open pit mines and quarries. It goes

hand-in-hand with the blasting operations to ensure adequately broken material for the

excavation equipment employed. In mining, all the unit operations are interrelated.

However, drilling and blasting are of utmost importance. Optimization of the other

procedures, such as, loading, hauling and crushing operations, depends upon the

desired fragmentation. The economics of these interrelated procedures are strongly

dependent on the drilling and blasting operations, which in turn are directly

responsible for providing the desired rock fragmentation. Therefore, it is critical to

analyze the economics of the drilling and blasting design. The drilling effectiveness is

highly dependent on the quality of drill evaluation [1, 2].

Drilling a hole in the ground with a machine is one of the most common, necessary

and important operations in geotechnical engineering and in the construction and

mining industries. It has long been accepted that, besides its primary purpose, drilling

itself can also be considered as a measurement and in situ technique for ground

characterization [3].

The importance of drilling in mining Engineering as it is an essential and

integral process of mineral exploration to present a clear picture of extent of any ore

body, its mineral content, and the stratigraphy or to confirm any geological or indirect

geological interpretations‎ of‎ what‎ is‎ laying‎ below‎ the‎ earth’s‎ surface.‎ ‎ The‎ type‎ of‎

strata and structure to be drilled has a significant influence on the drilling performance

of a bit. Resistance to penetration, resistance to the shearing action of the bit in

2

rotation and the degree of abrasiveness are the properties that would be expected to

have the greatest influence. The prediction of the penetration rate for the cost estimate

becomes a common problem in mining engineering. However, it is important to note

that the prediction of physical and mechanical properties of the rock formations from

drilling rates may help the mining engineer to control the changing characteristics of

the formations. After a hole is drilled, geophysical measuring instruments are

lowered on steel lines into the mud-and water-filled hole. Characteristics of the rock

such as its conductivity of electricity, other electrical properties, its radioactivity

(using gamma ray log), and porosity (holes in the rock) can all be measured. [4-6].

Cost of drilling is directly related to the performance of drill bits, the drilling

cost is controlled to a large extent by the drilling rate which is heavily influenced by

the wear condition of the bit. Wear may be defined as the removal of material from

solid surfaces as a result of relative sliding motion at the contact surface. Life of drill

bits and bit replacement cost as well as bit maintenance cost often cannot be perfectly

predicted because the factors influencing them are not easy to determine [7, 8].

Geology and rock drilling are more important to the civil Engineer at all stages

in a project; at the planning stage it controls the choice of site and determines the form

of structural work; for example, suitable drills to be chosen and tactical problems to be

solved. The most important in the context of rock drilling and estimating are

concerned with rock structures, map reading and water flow. Bore holes are drilled in

civil Engineering for industrial construction, making surveys of high-way layouts, for

investigation of the soil at the site of construction of dams, bridges, industrial plants

and houses. In addition to this, a good many bore holes and wells are put down to

provide for water supply of industrial and civil installations [[9, 10].

In this present work diamond core bit was used to study some drilling parameters

and their effect on drilling rate as a tool to predict the rock type to be drilled,

experimental work was carried out in the Department of Mining and Metallurgical

Engineering, Faculty of Engineering, Assiut University. Three categories of rocks

were used in this study (sedimentary, metamorphic, and igneous): Sedimentary rocks

3

were represented by five types of limestone namely: from the quarry of Assiut Cement

Company, northwest of Assiut, Samalout Formations from the quarry of Beni khalid,

east of Samalout in Minia, Issawyia limestone, east of Sohag, Mankabad limestone,

north of Assiut and Zaraby limestone, southwest of Assiut. Metamorphic rocks were

represented by two types of marbles namely: black and white marble, collected from

Wadi Al-Miah, Idfu - Marsa Alam road, from Gabal El- Rokham and El- Sowikat

respectively. Igneous rocks were represented by two types of granites namely: black

granite from Aswan and pink granite from Wadi Allaqi, Aswan quarry respectively.

The locations of these collected rock samples are shown in the map Figure 1.1.

Figure ‎1.1: Location of map of the studied rocks

4

1.2 The specific objectives of this study

1. To study the effect of the drilling parameters such as weight on bit (WOB), bit

type and its condition (new and used), and rotary speed on both rate of

penetration (ROP) and specific energy (SE) consumption of the diamond core

drill.

2. To obtain the optimum weight on bit (WOB) and rotary speed that give high

values of rate of penetration (ROP) and low values of specific energy (SE) in

three categories of studied rocks under test conditions.

3. Using some drilling parameters as a tool to predict the different Categories of

rocks.

5

CHAPTER 2

2 LITERATURE REVIEW

2.1 General

Geologists drill holes into the rock massif for several reasons. Probably the

greatest number of wells are drilled for water and these are the ones most people are

familiar with. But, usually very little rock information can be derived from them

because they are either too shallow or barely drilled into bedrock. They are less than

100 feet (30 meters) deep. Many shallower holes are also drilled to look for coal.

Additionally, state and federal geological surveys drill holes to study the rock and to

evaluate the occurrence of coal, gypsum, limestone and metallic minerals. It is

important to determine what kind of rocks are there and how they were formed. The

deepest well in the world is in Russia and is about 35,000 feet (7 miles, 10 kilometers)

deep [6].

The cycle of production in surface or underground mining includes the

following main operations: drilling, blasting, loading and transportation. Because

drilling and blasting are the primary operations in mining, they have a great effect on

the efficiency of carrying out the next operations. Moreover, they contribute about 20

to 40 % of the total cost of all mining operations [11].

Drilling is the culmination of the mineral exploration process where the third

dimension of a prospect, the subsurface geometry, is defined. Drilling provides most

of the information for the final evaluation of a prospect and will ultimately determine

if the prospect is mineable. Geochemical analyses of the drill samples provide the

basis for determining the average grade of the ore deposit. Careful logging of the drill

samples helps delineate the geometry and calculate the volume of ore, and provides

important structural details. The two principle types of drilling are diamond core

6

drilling and reverse circulation drilling (or RVC drilling). One of the most critical

decisions that must be made prior drilling a well is the selection of casing and bit

programs. This has an important bearing upon drilling economics because it dictates

the size of rig the contractor will use and also influences the number of days that will

be required to drill the well [12, 13].

Roy et al. [14, 15] found that, the success in making the cheapest hole must be

followed by evaluating drilling performance, and said that the minimum cost of

drilling any formation depends upon the ability to achieve the optimum advantageous

application between the following factors:

Average bit penetration rate and bit type and size.

Rig cost per day and drilling equipment.

Drilling fluid and rotary speed.

Bit purchase or rental cost.

Average Cost per foot = [(

⁄ ) ( ) ( )

] (‎2.1)

The drillability of rock decreases with increasing depth of the hole. Deep rock

will be more compacted and, therefore, harder to be drilled than the shallow rock of

the same type [16].

2.2 Historical Developments

No one knows exactly where the first well was dug; it may have been a shallow

depression in the earth, carried out by the primitive man with bare hands. The ancient

Egyptians have been said that they used corundum dust or pebbles in order to bore

holes in porphyry [17].

The Chinese in the year 1700 BC learned how to drill several hundred feet

through very abrasive and strong limestone to reach fresh water supplies. Also

Chinese are often quoted as drilling deep holes in loess, by the repetitive lifting,

7

dropping and rotating of coupled bamboo rods. Beside the Chinese practiced,

percussion drilling as deep as 1200 meters to obtain salt and water [9, 18].

Trevithick (1810-1820) in Britain built a steam–driven rotary rock drilling

machine. In 1818, the development of agriculture of French Government appropriated

many of drilling wells to the beds of artesian water, which were believed to be deeply

beneath the city of Paris. Isaac Singer (1830-1840) in U.S.A., has developed steam

churn drill. From (1850-1860) drills with a power stroke were invented. Burleigh

(1860-1870) in America designed a commercial piston drill. So that compressed air

was used as operating medium for rock drills [9, 18].

Churn drill or Cable –Tool – Drills were first used for drilling oil wells in

1860’s,‎but‎were‎ later‎ replaced by rotary drills, which more efficient at drilling than

the deeper holes that were required in petroleum exploration. In 1862, the use of

diamond tools started when George Leschot, a Swiss engineer developed the first

drilling machine and diamond-tipped bits in France. Toothed roller cutter bit were

used in America. Ingersoll (1870-1880) in America improved diamond rock drill and

invented the tripod, to drill holes over 2200 ft. (670m); Rand (U.S.A.) developed

mining drills; Hall (U.S.A.) produced the Sullivan diamond drill [9, 19].

In (1880-1890) a diamond – drill hole reached 5734 ft. (1750 m); Holman

(G.B.) produced a rock drill. In (1890- 1900) Commercial pneumatic rock drills were

being produced by Cleveland, Chicago pneumatic, Gardner- Denver, Hardy- Pick,

Holman Bros., Ingersoll-Rand and Others. In 1900, Leyner invented the hammer

drill, the hollow drill steel and the shank, which still bears his name. In (1900-1910)

Huges (U.S.A.) perfected the Tricone bit "Roller cone bit" [9, 19].

An interesting well was dug in ancient time in Cairo, Egypt and is still

producing‎ water‎ as‎ 1900.‎ ‎ It‎ is‎ well‎ known‎ as‎ “Joseph’s‎ well”. Ingersoll – Rand

introduced two new 600 series crawler drills at MINExpo 2000. Its ECM-660 drill

sinks holes from 3 – 4 ⁄ in. diameter and is equipped with a Montabert HC120

8

hydraulic drifter drill. Hole cleaning has been enhanced with a GHH-Rand air

compressor that delivers 310 cfm at 140 psi and a high vacuum dust collector [17, 20].

A diamond core drill was made by the Sullivan Machinery Company (1900-

1925), which was driven by 20 steam engine. The depth capacity of drill was

between 360 to 763 meters of 72 mm hole diameter, recovering a 51 mm core, the drill

weighted 3580 kg. It was realized that steam engine powered drills were much too

large and heavy. It gives some indications how rapidly the design of the drill was

developed in those days [17, 18].

In 1930, Rotary machines of conventional table type, prior to the early 1930,

had always been related at speed varying, generally, from 30 to 60 r.p.m. With the

introduction of diamond drill type machines for oil well drilling, the increased

efficiency of higher rotating speed was realized speed varying from 200 to 400 r.p.m.

In mid-1930’s‎ rotary‎ machines‎ were‎ redesigned to accommodate the higher speed

rotation being introduced. Bits and drill pipes were improved; drill collar strings were

increased in length, weight and balance. Presently rotary drills in different

combinations are being used for drilling oil/water wells and blast holes [17].

Tungsten carbide was first used in drill bits (Germany) in (1920-1940). In

(1940-1966) Tungsten – Carbide bits perfected; invention and general acceptance of

down – the- hole drills; introduction of turbine drills. Rock drilling techniques have

undergone rapid development. One of the reasons for this, and not the least important,

is the introduction of new drilling tools equipped with tungsten carbide cutting edges.

The high productivity of the modern mining industry and the building of large civil

engineering projects in this period would have been virtually impossible without the

aid of tungsten carbide tipped drilling tools [9, 17, 19].

Diamond hand – held cutters developed by Chinese hundreds of years ago. It

was the ability to pound a single diamond stone into a suitable brass alloy, which

composed a tool holder. With this invention, they had a method to hold the diamond

and manually impact the rock without shattering the brittle diamond. Many workers

9

would excavate man-sized holes several hundred feet down to gain access to fresh

water. Rotary drilling has been used in surface mining for many years. Its principal use

is for primary blast holes drilling. In this use, holes in the range from 4 to 15 in. in

diameter are drilled in over burden and massive ore bodies for large initial blasting

operation, rotary drilling with diamond bits is used for exploration. Tricone bit 50

years ago, up to 98 percent of the drilling was performed with a more robust roller

cone bit. The introduction of the natural diamond bit 40 years ago resulted in up to 2

percent of the petroleum footage being drilled with relatively small diamond cutters

[21, 22].

Since, the introduction of polycrystalline diamond compact (PDC) bits in the

mid-1970’s‎ their‎ application‎ in‎ the‎ mining‎ and‎ oil‎ industries‎ has‎ represented‎ a‎

significant advancement in drilling technology. Until 1986 core drilling was carried

out using natural diamond surface set core bits operating at a much higher speed of

300 rpm. Early in 1987, Foraky approached Diamond Boart SA, SYNDAX-3 instead

of natural diamond, in the core bit. SYNDAX-3 increased penetration rates and tool

lives by 100% [19, 23]

Polycrystalline diamond compact (PDC) diamond is no longer thermally stable

at 700 C0. Therefore, one limiting factor for the use of PDC drill bits is petroleum

drilling applications with higher cutter temperatures associated with drilling abrasive

and hard formations. Today, 65 percent of the petroleum footage is drilled with a roller

cone bit and 35 percent with a PDC diamond cutter. About 20 percent of the drilling is

carried out by using carbide insert roller cone bits. Roller cone bits are used to do the

bulk of the drilling in geothermal wells, even though their lives are severely shortened

when the formation temperature exceeds 3500 C0 [21, 24].

The drilling industry, in common with other industries is becoming

increasingly competitive. Machine manufactures and operators are continually

exploring ways of reducing costs and enhancing productivity through the application

of automatic control. Formalized procedures for performance optimizing appeared in

10

the‎ early‎ 1950’s‎ and‎ since‎ then‎ many‎ technical‎ advances‎ have‎ contributed‎ to‎

development of improved techniques, and introducing automated rigs so that, drilling

costs improved. One of the earliest large- scale systems for the automatic optimization

of rotary refining company. Many companies now offer computer- controlled drilling

systems as well as a wide range of rig sizes and drilling techniques [19, 25].

2.3 Drilling methods

The two drilling methods rotary and percussion are still the basis of all

conventional drilling techniques. There are cable tool percussion, rotary percussive,

down the hole hammer, continuous flight type auger, turbo drill, standard rotary

drilling air, mud or reverse circulation and high speed diamond core drilling, etc. The

various methods of drilling are discussed in the following parts [19].

The type of equipment used depends upon the site, geology, hydrology,

equipment available, and monitoring design. Control of cuttings and other potentially

contaminated materials at the drill site may influence drilling method selection.

Depending upon equipment availability and site geology, more than one method may

be combined to complete a particular monitoring well installation [26]. Some of

conventional drilling methods are introduced in the following Fig. 2.1.

2.3.1 Percussion drilling

There are several methods for drilling rocks, but the most universal, and when it

comes to drilling very hard rock the only efficient one, is percussive method, this

drilling technique is based on generating periodic impact forces in order to enhance

dynamic crack creation and propagation in the brittle type of drilled materials. The

percussion drills consist basically of a hammer unit is driven by compressed air. This

hammer unit imparts a series of short, rapid blows to the drill steel or rods and at the

same time rotates them. The drills vary in size from small hand- held rock drills for

drilling charge holes to large truck- mounted rigs capable of drilling large diameter

11

holes to depths of hundreds of meters. Percussion drilling is a rapid and cheap method

but suffers from the great disadvantage of not providing the precise location of the

samples, as in the case of diamond core drilling. However the price of percussion

drilling is about one third to one half of that for diamond drilling. Percussion drilling

is the technique that is most often used in evaluating deposits and for the drilling of

“blast‎holes”‎in‎mining‎business‎[19,‎27,‎28, 29].

Figure ‎2.1: different drilling methods [19]

Percussive Rotary

Churn

DTH

Top

Hammer

With bottom

engine

Non-Core

Diamond Rotary

Percussive

Auger

Reverse

Core

Wire

Line

Conventional

Or

Standard

Double – tube

core barrel

Triple- tube core

barrel

Single – tube core

barrel

Drilling Methods

Conventional

Or

Standard

12

2.3.1.1 Churn or Cable- Tool- Drilling Method

Cable-tool (cable percussion) drilling is the oldest, simplest, and most reliable

technology available of water well drilling. This drilling technique is a portable

equipment, usually mounted on four wheels and driven by steam, diesel, electric, or

gasoline -powered engines or motors and involves chipping and cutting earth materials

by lifting and dropping a heavy, solid chisel- shaped bit, suspended on a wire rope

(steel cable), that is lifted and dropped to break up and remove cuttings from the

bottom of the hole. Steel casing is often used to keep the hole open during drilling in

unstable materials. Casing also is used to isolate potentially contaminated strata.

Figure (2.2) shows the cable tool drilling machine [26, 30, 31].

Figure ‎2.2: Cable tool drilling [30]

It utilizes the principle of free falling weight to deliver blows against the

bottom of the hole by the movement of the spudding beam. This process of lifting and

dropping (as many as 60 times a minute) of percussion drill develops the mechanical

energy that breaks up the underground formation and bores the holes.

A tight line accompanies drilling in this system so that the bit strikes the bottom

of the hole when stretched. Because of the elasticity of the cable, stretching causes it to

13

unwind and recover when tension is released. The hole cleaning is performed by

retracting the drilling tools and running a bailer to the bottom of the hole. Tools for

drilling and bailing are carried on separate lines or cables spooled on independent

hoisting drums. Cable tools plants are limited to vertical holes only as penetration

depends upon gravity only. Today churn drills are mainly used for water well drilling

and they may be useful in mineral exploration. Churn drills can be useful in

exploration work for sampling soft formations up to depths of 100 – 150 ms. Costs are

comparable to and may be less than percussion drilling. The main disadvantage is that

it is very slow, but if time is not important and if only vertical holes are required,

churn drilling is worth considering [19]. The efficiency of churn drilling was studied

with consideration of wave energy radiation into the rock. In this process, a hammer

with cutters on its front subjects the rock to direct impact [28].

Cable tool has many advantages such as [26, 29, 32]:

Allows for easy and accurate water and soil sampling; easy detection of water

levels during drilling; can detect very thin permeable zones.

Driven casing seals off formation, minimizes threat of cross contamination in

pollution investigation.

Usually successful in drilling through boulders.

Unrestricted as to hole depth, diameter, and geologic and hydrologic conditions.

Produces minimal volumes of cuttings which are easily contained; minimal or

no well development necessary.

Little or no outside drilling fluids necessary.

It is possible to drill in formations where lost circulation is a problem.

Cable tool has little disadvantages such as [26]:

Extremely slow rate of drilling.

Normally necessary to install one or more strings of steel-drilling casing.

14

2.3.1.2 Down -The- Hole hammer (DTH)

Down the hole drilling (DTH) is a rotary percussive drilling technique that is

used in medium to hard formations [31]. In this drilling technique, the motor is inside

"down" the hole, and this advantage makes waves not have to be transferred over

increasing distance as the hole depth increases [33]. The down -the-hole (DTH)

hammer drill has been used widely in mineral deposit exploration, the mining industry,

hydrological drilling and engineering construction, because it has the characteristics of

high efficiency, good drilling quality and low cost. At present, cemented tungsten

carbide is adopted as the cutter of button bits used in the down -the-hole (DTH)

hammer drill, but lower abrasion resistance and short service life of cemented tungsten

carbide seriously affected the drilling efficiency of down -the-hole (DTH) hammer

drilling in an extra hard formations [34]. The hammer unit is lowered into the hole

attached to the lower end of drill rods to operate a non-coring, tungsten carbide tipped,

drill‎ bit‎ sometimes‎ known‎ as‎ a‎ “button‎ bit”.‎ ‎ Holes‎ with‎ a‎ diameter‎ of‎ up‎ to‎ 20‎

centimeters are possible, with penetration depths of up to about 200 meters, but depths

of around 100 - 150 meters are more common [27].

The rods generally vary in diameter from 85 to 115 mm, and bits from 100 to

200 mm. The rigs vary in weight from 1.5 to 3.0 tones and entire truck mounted units

complete with compressor and ancillary equipment may weigh 5 tons or more. Depth

capabilities of up to 250 m are possible with some types, though most rigs are only

capable of reaching depth in the range 100 - 125 m [10, 19]. Figure (2.3) shows down

– hole hammer schematic [31].

Flushing of the drill cuttings from the hole to the surface is carried out using

stream of compressed air; therefore a constant and reliable source is required during

operation. This is usually supplied by a high output air compressing system, which

varies in size depending on the scale and portability of the drilling. Sometimes special

foaming agents are available and used to assist in flushing out holes in wet ground.

Down-the- hole hammer drills are mainly used for shot hole and water well drilling

and are not commonly used in mineral exploration [19, 27].

15

Drilling with water driven down-the- hole (DTH) hammers is a recently

developed method for competitive production of boreholes [35].

Figure ‎2.3: Down-the-Hole hammer schematic [31]

2.3.1.3 Top hammer drill

In this type of drill, both the percussive and rod rotation are provided by a

hammer unit powered by compressed air at the top of drill system, and the energy to

the non-coring drill bit is transferred through the drill rods. This type of system is

usually smaller than down –the- hole drills and they are used for holes up to 10

centimeter (cm) in diameter and drill up to depths of 100 meters (m). Usually this type

of drill rig is only employed to depths of no more than 20 meters. Most units only use

light portable air [28].

16

The hammer unit is track mounted on the rig and is moved up or down by a

chain feed, and the holes that are drilled by top hammer drills are smaller in

diameters than those drilled by down-the hole drills, with rods varying in diameter

from 38 to 45 mm and bits from 64 to 102 mm. For using in mineral exploration the

drills are usually mounted on trailers, truck or large tractors, and for using in quarries

open pits drills are sometimes mounted on truck- laying vehicles and are then referred

to as crawler drills. The latest machines are all hydraulically controlled and are easily

operated by one man and a helper. Most percussion drills only use air for flushing the

hole, but some machines use equipment designed for water circulation and flushing.

For mineral exploration drills with water flushing facilities are far superior. The

samples produced by percussion drills vary from fine dust to small chips depending

upon the nature of rock being drilled. Coarse, friable grit, for example, may result in

samples with high proportion of coarse fragments, whereas samples from massive

limestone may be largely dust. Whatever rock being drilled, however, it is usually

possible to recognize rock types from the sample fragments as there are always fair

proportions ranging in size from 1.0 to 2.0 mm. Although, this system is generally

limited to drilling small diameter wells through rapid clay and sand formations, but it

gives accurate samples. For any percussive drilling process, a hammer with cutters on

its front subjects the rock to direct impact [10, 19, 28, 36].

2.3.2 Rotary drilling

In the rotary drilling method, action is accomplished by rotating a drill pipe by

means of a power driven rotary table or hydraulic powered top head drive, with a bit

attached to the bottom of the pipe. The bit cuts and breaks up the materials as it

penetrates the formation. Drilling fluid for mud is pumped through the rotating drill

pipe and through holes in the bit. This fluid swirls in the bottom of the hole picking up

material broken by the bit, then flows upward in the space outside the drill pipe,

carrying the cuttings to the ground surface and clearing the hole. Rotary drilling with

mud is the most widely used method for water well construction. A rotary drill rig has

three functions: rotating the drill string, hoisting the drill string and circulating the

17

drilling fluid. A bit is rotated against the formation while mud is pumped down the

drill pipe, through ports in the bit, and back to the ground surface through the annulus

between the drill pipe and the borehole wall [37, 38]. Rotary drilling can be subdivided

into rotary cutting and rotary crushing, rotary cutting creates the hole by shear forces,

breaking‎ the‎ rock’s‎ tensile‎ strength,‎ while,‎ rotary‎ crushing‎ breaks‎ the‎ rock‎ by‎ high‎

point load, accomplished by a toothed drill bit, which is pushed downwards with high

force [39].

Rotary systems work well in soft formations, the drilling rate decreasing as

rock hardness increases. Rotary drilling system relies upon high rotational speeds and

thrust without percussion to achieve the desired effect and outputs. Heavy drill collars

are sometimes needed to add extra thrust to the bit. Rotary machines are usually large

self-contained hydraulically powered units with sufficient weight to provide the thrust

on the drill bit to drill the hole. The harder the rock the greater the thrust required, the

heavier the machine, the greater initial capital outlay, the higher the operating costs.

The same factors apply when hole diameters are increased. Excessive thrusts can lead

to deviation of borehole particularly when drilling at angles in bedded formations [10].

The rotary drilling method has the following advantages [26]:

1. Quite fast efficient means of drilling; several hundred feet of bore-hole

advancement per day is possible.

2. Capable of drilling to full range of depths and diameters necessary for

monitoring- well installation.

3. Direct-mud rotary effective in all hydrologic conditions.

4. Rotary drilling easily supports the telescoping of casing to isolate drilled

intervals and prevent cross contamination of strata encountered during

drilling.

5. Geophysical logs such as self-potential and resistivity (which must be run

in an uncased bore hole) may be run before well installation, and

6. Efficient rigs offer several hundred feet of hole per day.

18

The rotary disadvantages are:

1. Potential cross contamination of strata exposed to the fluid circulation

during drilling, so that drill fluids may invade permeable zones.

2. It has some inherent defects for monitoring- well installation.

2.3.2.1 Reverse circulation drilling

The reverse circulation rotary drilling operates by the same general principles

as direct mud- rotary except that drilling fluid is pumped down the drill rods and

returns with the drill cuttings up through the annulus. The reverse circulating rotary

method is best suited to drilling in relatively stable to consolidated formations.

Reverse circulation rotary technique is very fast and efficient means of drilling. Rigs

are equipped and staffed so that they can drill several hundred feet of hole per day.

This drilling method can reach several thousand feet in depth and create hole

diameters up to approximately 17 inches [26]. This reverse type of drilling is a suction

dredging method in which cuttings are removed by a suction pipe. The rig includes a

large – capacity centrifugal pump, a drill pipe, and a bit, which resembles a dredge

[40].

There are two types of reverse circulating drilling available today. Both of

these methods use the exact same dual drill pipe. The only difference is the hammer

that attaches to the pipe. The two types of reverse circulating drilling are: Center

sample and the conventional reverse circulating drilling. The center sample reverse

circulating drilling is the newer of the two methods, and uses special center sample

hammer. The advantage of this method is the sample goes immediately into the drill

pipe without having to travel up the side of the conventional hammer. Figure (2.4)

shows the reverse circulating drilling system [41, 42].

19

Figure ‎2.4: Diagram of Reverse circulation drilling system [42].

2.3.3 Auger drilling

It is another drilling method employed in loose formations. Auger drills are

widely used for making vertical and inclined (angling) drill holes mainly in collieries

(coal, clay, stone, soft limestone), and when working non- strong kind of rock (marl,

soft limestone) used in construction. The auger drilling practices are characterized by

the feed force, rotation speed of the drilling tool and efficiency with which the cuttings

are moved from the drill hole. Large holes in soil and soft rock can be drilled rapidly

and inexpensively by mechanized auger drilling. The major advantages of this method

are as follows: (I) a very high rate of penetration can be achieved; (II) a large spoil is

obtained in short time; (III) no flushing medium is required; (IV) noise level is very

low. The common applications include, prospecting foundations tests, soil

reinforcements, fence posts, and some type of well drilling and blast holes [19].

Augers are usually hand-held‎ or‎ truck‎mounted‎ drills,‎which‎ have‎ rods‎with‎ “spiral‎

shaped‎flights”‎used‎ to‎bring‎soft‎material‎ to‎ the‎surface.‎ ‎Augers‎vary‎ in‎size,‎ from‎

those to dig fence post sized holes, up to large ones over a meter in diameter. Augers

are light drills and are incapable of penetrating either hard ground or boulders [28].

20

2.3.4 Diamond drilling

Diamond core drills are exploratory machine primarily, but also fill a gap in

blast hole drilling not converted by other classes. Also core drilling can be utilized

for: Sampling in situ, drainage of mine workings, ventilation, sand filling, rock

mechanics instrumentation, gas and oil drilling, proving the quality of structural

concrete of dam sites, rock bolting and drill holes for ground stabilization. Diamond

drills are used for holes varying from few centimeters to many thousands of meters in

oil well drilling [5].

To produce a core sample, diamond drilling is chosen because they are used as

surface rigs and underground, by the oil, civil engineering, quarrying and mining

industries and for holes varying in depth from a few inches (cm.) to many thousands of

feet (meters) in oil well drilling [10, 19]. This drilling system is most versatile of all

the methods, and it is designed specifically for the resource exploration industry and to

collect a sample in the state that is found. Successful diamond drilling is both art and

science, that requiring the proper understanding of how to use drilling speed and

pressure, coolants, and drilling accessories to maximize production efficiency, drill life

and product quality [28, 42, 43, 44].

Diamond drilling techniques are used when precise, circular cuts are needed.

Holes of almost any diameter from 6mm for items such as anchor bolts up to 1.5 m for

pipe work are easily drilled. It is also commonly used for drilling holes to route cables

or place anchoring bolts, to install load carrying devices or dowel bars, or for analysis

of structures, rock or strata. Diamond core drills have super sharp bit teeth and long

bit life [45, 46].

Today there are two main types of diamond drilling [10]:

Standard or conventional diamond drilling.

Wire- line diamond drilling.

In the Conventional diamond drilling type the sample is cut by a diamond

armored drill bit, stored in the inner barrel of drill pipe and then the pipe is brought to

the surface and then the core is removed. But, in wire line diamond drilling, the most

widely used and time effect method, the inner tube is hoisted to the surface through the

21

drill rods without the need to remove or withdrawing the rods from the hole. Using a

device known as an overshot, this is lowered down the inside of the rods on a cable

and locks onto the top of the core tube. The action of the overshot locking onto the

core tube causes latches that hold the core tube in the core-barrel to be withdrawn thus

freeing the core tube so that it can be hoisted to the surface [10]

Polycrystalline diamond compact (PDC) bits have proved successful in drilling

soft to medium strength rock formations because they achieve high rates of penetration

(ROP), while also maintaining long bit life. The development process has progressed

so that today a large amount of footage is drilled with PDC bits [47].

Non-core drilling methods generally have the advantages of lower costs than the

core drilling methods. When the core is not required, a non-core drilling method is

preferable. Non –coring methods are mainly used for the following [48]:

Geophysical logging.

Obtaining samples for assay and metallurgical testing.

Defining ore contacts in extensive sedimentary deposits.

Drilling through thick section overburden, and

Hydrological testing.

2.3.5 Heavy rotary blast hole drilling

Rotary blast hole drills are widely used for overburden removal all over the

world. A typical example may be cited as that, more than 100 million m3

of over

burden blasted annually in five Turkish open pit mines with a total annual drilling

length of around 1.65 x106

m. The common blast hole diameters range from 38 to 48

mm.[49, 50].

In surface/quarry mining, large diameter drilling equipment gives a high

productivity rate. Heavy rotary blast hole drilling is far superior to down-the-hole or

percussive methods in broken ground and in ground consisting of alternating bands of

22

hard and soft rock or rock with substantial clay bonds. The advantages of this drilling

type are as the follows [48]:

It is preferable in many sedimentary rocks.

It is an alternative in hard rock; provided that the drills of adequate

large holes are acceptable.

It gives a wider range of hole size and may be used to greater depths

In‎“bad”‎ground‎it‎may‎be‎the‎sole‎economical‎method‎[48].

The factors to be considered in selecting a rotary blast hole drill rigs are:

mounting, power source, rotation pull down system, air volume requirement, most

inclined drilling capability, dust system, water, foam injection and noise suppression

[47, 49].

2.3.6 Rotary- Percussive drilling

In this method the penetration of the drill bit occurs due to resultant action of

both percussive and rotary movements. The rotational movement applies free on the

bit end to break the bond, holding the rock particles, while percussive action produces

longitudinal impact on the rods resulting in penetration of bit driven into rock. Rotary

Percussive drilling hammers are applied with an impact power of about 15 to 20 KW.

The main shortcomings of this type are short bit life, low output, and dust formation

[48, 50]. The optimum productivity for this method is possible by combining

advantages of both rotary and percussion drilling. The percussive – rotary drill was

developed first by the Salzgitter Company and then by Hauser and Nusse &Grafer.

This type of drilling machine had been mainly used in underground works [51].

A rotary – percussive rock drill was tested for wear under dry conditions when

drilling granite. Granite caused more rapid wear of drill bits than other rocks.

Rotary- Percussion drilling method is applied in very hard rocks, such as granite, the

only way to drill a hole is to pulverize the rock, using a rapid - action pneumatic

hammer,‎often‎known‎as‎a‎“down-the-hole‎hammer”‎(DTH).‎Compressed‎air‎is‎needed‎

to drive this tool. The air also flushes the cuttings and dust from the borehole.

23

Rotation of 10-30 rpm ensures that the borehole is straight, and circular in cross-

section. The advantages of rotary-percussion drilling are: drill hard rocks, possible to

penetrate gravel, fast, and operation is possible above and below the water-table. But

the disadvantages of this method are: higher tool cost than other tools of drilling

methods, air compressor required, and requires experience to operate and maintain.

[52, 53]. The prediction of the penetration rate (PR) of rotary – percussive drill is very

important in mine planning. Total drilling costs could be estimated by using

prediction equations to select the drilling rig type, which is best suited for given

conditions. The drillability of rocks depends on many factors. Bit type and diameter,

rotational speed, thrust, blow frequency and flushing are controllable parameters [54].

Table (2.1) shows drilling methods for the various ground conditions [48].

Table ‎2.1: Drilling methods for the various ground conditions [48].

Rock type Drilling method Remarks

Soil,

sand/gravel

Auger

Rotary

Sometimes temporary casing required

Temporary casing or mud additives required.

Soil, silty/clay Auger

Rotary

Mostly best choice

Temporary casing or mud additives required.

Rock, medium

hard

Rotary

DTH

Roller bit, sometimes needs mud additives

Large compressor required.

Rock, hard to

very hard

Rotary

DTH

Top hammer

With rock bit or hard- metal insert button bit, very slow.

Large compressor required.

Special equipment, depth range to 70ms.

Rock, core

sampling

Diamond Mostly best choice for sampling in site, quarry and

geological investigation, proving the quality of structural

concrete.

Rock under

over burden

ODEX

Or similar

In combination with DTH.

The following general guidelines are used to determine which drilling method is

necessary for the drilling operation [48]:

For small diameter shallow blast holes, jackhammer or truck mounted drills

are usually used.

For blast holes up to 6 inches and about 50 feet deep, track mounted,

percussion drills are used.

24

For drilling holes from 6 to 12 inches, from 50 to 300 feet deep, rotary blast

hole drills are usually the best choice, but this is affected by the type of rock.

If cores from 3 inches up to 8 inches are desired, diamond drilling is the best

choice. The diamond drill can drill faster and is not limited by the direction.

2.4 Major factors influencing penetration rate

Penetration rate is the factor that has a major influence on the productivity and

consequently, on the overall cost per unit, and is influenced by geological parameters,

machine parameters and operating parameters [55].

Drilling rate is one of the main factors affecting drilling cost. The overall

performance of any drill bit is complex and is affected by numerous factors which

include operating parameters of the bit, formation properties, bit design and type, wear

characteristics, drilling fluid properties and flow mechanics, hole characteristics,

capacity of the drilling machine, time, climate and operator or crew efficiency.

However, the principal factors that require consideration in predicting drilling rates are

the operating parameters of the drill bits and the penetrated rock characteristics [47].

The most important factors that affect the rate of penetration are [19]:

Weight on bit (thrust) and rotary speed,

Bit type and condition,

Rock properties (Formation characteristics), and

Fluid properties (circulation).

One can conclude that each rock type has different drillability values depending on

the drilling system and the bit used. Therefore, the only acceptable way to determine

the drillability of a rock is to drill it. Drillability values have, therefore, been obtained

using rotary drilling system for a wide range of rock types from different areas [11].

25

2.4.1 Weight on bit (WOB) and Rotary speed (RPM)

Weight on bit, WOB, is amount of the axial force applied to the bottom-hole.

Since bit weight and rotational speed considerations are interrelated i.e., an increase in

one usually necessitates a reduction in the other for minimum cost drilling. In soft

formation doubling of either bit weight or rotational speed will double the drilling rate.

In hard formation when bit weight and rotational speed are increased the rate of

penetration is increased too [19].

The required thrust depends upon the drilling method, the size of bit, the

sharpness of cutting edges, the resistance of rock and pressure of flushing medium that

tends to lift the bit off the rock. In rotary drilling, penetration speed is directly

proportional to the applied thrust. In spite of this there are limitations to the degree of

thrust that can be applied because over thrusting tends to cause rods to bend and hole

to deviate. On the other hand, under thrusting produces excessive bit wear in all forms

of rotary drilling, diamond, drag and roller bits [11].

2.4.2 Bit type and Condition

The bit type selected and the design characteristics of the bit have a significant

influence on ROP. Tooth length; number of cutters; cutter exposure or blade standoff;

size, shape, surface, and angle of the cutter are some of the many bit characteristics

which affect ROP and bit performance. Bit condition, specifically the bit wear state,

has an influence on the effectiveness of drilling; and increased wear reduces ROP and

bit performance [19, 48].

Selection of bit type has a large effect on the penetration rate. It plays an

important role to determine the performance of a drill with respect to efficiency.

Continuous research and experimentation have resulted in bit designs that provide a

specific bit types for a wide range of drilling conditions. These bits are classified into:

diamond bits, carbide bits saw tooth and rotary drill bits. Diamond bits can be

classified according to the type of rock to be drilled as: surface-set diamond bits,

26

impregnated diamond bits, polycrystalline diamond (PDC) and strata-pax drill blank.

According to the profile and design of the crown: coring and non-coring bits.

According to the drilling technique used: conventional drilling diamond bits and wire

line- drilling bits. The carbide rotary drill bits are classified into coring and non-coring

bits and they include: standard carbide bits, pyramid carbide bits and saw tooth bits.

Non- coring includes: roller and drag bits. The following Fig. 2.5 illustrates the

different types of drilling bits [19].

Figure ‎2.5: different types of drilling bits [19]

2.4.3 Rock properties

Rock properties are the unalterable factors that affect the rate of penetration.

Fundamental studies in rock mechanics led to better define rock properties. Formation

Bit Types

Rotary bits Percussive bits Diamond bits

Roller Drag Blade Button type Core Non-core

Blade Replaceable

Three cones Two

Cross bits Flat with a

number of

TC inserts

X-bits

Chisel bits

Impregnated

Surface-set

Polycrystalline

Concave Taper Pilot

27

properties that have been investigated are: compressive strength, hardness and

abrasiveness, overburden pressure, porosity, pore pressure, permeability, elasticity and

rock temperature. As a general rule, rock strength and over burden pressure increase

with depth. At greater depths, the rocks are more compact and therefore, more difficult

to be drilled. The hardness and abrasiveness characteristics of a rock have an influence

on bit life. In general, penetration rate varies inversely with Compressive strength and

is directly proportional to porous or permeable rock formations [19, 47, 48].

The elastic limit and ultimate strength of the formation are the most important

formation properties affecting ROP; however, the mineral composition of the rock can

change the ROP. For example, Rocks containing hard and abrasive minerals can cause

rapid dulling of the bit teeth, and gummy clay minerals can cause the bit to ball up.

The rock would be drilled very slowly in either case [11].

2.4.4 Fluid properties (Circulation)

The properties of the drilling fluid highly affect ROP. Density, flow properties,

solids content and size distribution, and chemical compositions are some of the

properties, which have a high influence on bit performance. If a dense fluid such as

mud or water is used for circulation, the formation drilled is influenced by a

hydrostatic pressure that depends on hole depth and drilling fluid density [48, 56].

Water is the most commonly used drilling fluid, but when drilling in soft rocks,

it is found to be too erosive. In such cases mud, which consists of a bentonite-water

mixture is used. In blast hole drilling direct air flushing is used with three-cone rolling

bits because of greater penetration rate and longer life. To reduce airborne dust a

small amount of water is injecting into air stream. This air mist mixture agglomerates

the fine dust into large pellets, which can be collected more easily. The principle

functions of a drilling fluid are: carry cuttings from the hole, cool and clean the bit,

reduce friction and maintain stability of uncased holes [19].

28

2.5 Automatic optimization of drilling techniques

Optimization means obtaining optimal results by lowest drilling costs; many

experiments on drilling in different rock types were carried out in the laboratories and

in situ. These experiments have shown that the weight on bit (thrust), physical and

mechanical properties of the drilled rocks and rotation speed of the tool are the most

important factors affecting the optimization of the drilling system. The optimization

can be judged by considering some factors, including penetration rate, total time for

hole completion, percentage of core recovery, bit life, etc. It has been shown from the

previous experience and works on the drill rig that the thrust plays a major role in

affecting penetration rates and may be treated as the governing control parameter [48].

2.5.1 Drill productivity evaluation by monitoring

During the last decades, the use of microprocessor-based drill monitoring

equipment to permit scanning, measurement, processing and storage of drill

performance parameters has become an accepted technique. The equipment used for

monitoring was an integrated part of the drill rig. The drilling information was

collected for a period of time. During this time data were sampled, hours, minutes,

and seconds (h: m: s), drill-hole depth (m), penetration rate (m/min), rotation speed

(rev/min), thrust (KN), air percussive pressure (bar), and torque pressure (bar), were

recorded for every 10 mm of hole length. Improvement in the drilling cycle, resulting

in improved overall production. The monitored drill parameters were stored on an

ordinary 3.5 inch diskette in the monitoring instrument, which was mounted in the

operator’s‎cabin‎of‎the‎drilling‎rig‎and‎the‎diskettes‎were‎transferred‎to‎the‎office‎for‎

analysis [19, 48, 57].

2.5.2 Rock characterization by monitoring

Researches have shown that measurements of specific energy, in conjunction with

accurately known drill depths, can be used to indicate the location of strata boundaries

and voids. Percussive drill monitoring can provide detailed information on hardness,

fracturing and weathering of the rock mass. The major advantage is the speed at

29

which the result can be presented. Since, the data are monitored in digital form and

analysis on an ordinary computer only takes a few minutes, the method can be made as

an integrated part in a decision process. The recorded parameters are: time when data

are recorded, drill hole length, penetration rate, rotation speed, thrust, air pressure and

torque pressure. This technique has been used successfully in several mining and

underground applications, providing rock properties with high agreement with the

observed conditions [19, 58].

2.5.3 Measurement While Drilling (MWD)

Today all interpretation is done by software, allowing information to be

delivered to different centers in the mine. Measurement while drilling (MWD)

techniques can provide a useful tool to aid drill and blast engineers in open cut mining

[19]. Fig. 2.6 shows the measuring while drilling system (MWD) [59].

Driller

Driller software

Data reduction, analysis& display

Figure ‎2.6: schematic representation of the MWD system [59]

A high – speed data link provides faster communication from downhole

instruments to the surface and back again. Many aspects of the drilling process will

High Speed Data Link

MWD

30

improve if downhole and surface data were acquired and processed in real – time at

the surface, and used to guide the drilling operation. The main focus of this program is

to demonstrate the value of real- time data for improving drilling. While high - rate

transfer of downhole data to the surface has been accomplished before.

Demonstration of the benefits of measuring while drilling (MWD) based on a high-

speed data link will convince the drilling industry and simulate the flow of private

resources into the development of an economical high – speed data link for geothermal

drilling applications to control and improve drilling performance. Real – time data

achieves many benefits, such as, improving rock penetration rates, bit life, improved

drilling pressure, reducing drilling costs and gives us a better understanding of the

drilling process [59].

2.5.4 Rotary and Percussive drilling rate prediction models

Programming system facilitate rapid driving models and prediction equations,

for rotary – percussive drilling penetration rate. Prediction of the penetration rate is

very important in mine planning. Total drilling costs could be estimated by using

prediction equations. Also, one could use prediction equation to select the drilling rig

type, which is best suited for given conditions. The drillability of rocks depends on

many factors. Bit type and diameter, rotational speed, thrust, blow frequency and

flushing are the controllable parameters. On the other hand, the parameters such as

rock properties and geological conditions are uncontrollable parameters. Drillers try to

develop a model for drilling and blasting in open pits and quarries [60, 61, 62].

Prediction models seem to be promising and as per expectance. The recorded

test values show that the model equations are well suited to describe and distinguish

the all operating properties [62]. Today's, computer drilling simulator has been

modified and spreads all over the world. The starting point is to obtain field data that

is needed for simulation, these data were used as input for simulator in order to have

predictions of the rate of penetration as an output [63, 64, 65]. Environmental,

archeological and biological factors may place restriction or conditions on a site of

drilling. Disposal cleared material should be arranged and the use of drilling requires

31

planning and implementation prior to drilling. Developing an exploration program

requires a thorough knowledge of the design requirements, site conditions, drilling

equipment requirements and capabilities and rock properties. Drilling procedures

needed are based on the drilling sampling requirements [66].

The Ultrasonic / Sonic drilling / Coring (USDC) device opens new possibilities

for future sample return mission. Unlike conventional drilling rigs, USDC can core

even the hardest rocks. The device can be duty cycled without significant loss of

efficiency, this facilitating operation under low power. Unlike conventional drills, the

drilling head of the USDC does not have any gears or motors, it has only two moving

parts, and, thus, can be easily adapted to operations in a very wide temperature ranges.

The drilling tool does not require sharpening, its drilling speed does not decline with

time, and it does not rotate. USDC can core arbitrary cross- sections (square, round,

hexagonal), since conventional rotary drills and cores cannot meet these capabilities of

USDC [67].

2.6 Future perspective of drilling techniques

In 2001 a number of leaders from drilling industries met in Washington D.C to

discuss and develop a vision for future of drilling. The vision for 2020 includes [19]:

2.6.1 Safety and health

Use of autonomous drilling systems tools that will reduce the number of

workers needed in hazardous environments. These systems may include

robotics, remotely controlled technologies and computers.

Improved worker training to ensure safer drilling operations.

Reduce or eliminate noise, dust and vibration thereby benefiting both workers

and surrounding area.

In- situ management of toxic and waste materials thereby eliminating associated

environmental and health issues.

Drilling without the use of mud to avoid cleanup and disposal costs.

32

Unconventional drilling methods such as lasers, percussion drilling, microwave

drilling and deep sea drilling.

2.6.2 Productivity

Improvements in productivity will require an integrated systems approach to

drilling operations. The drilling industry in 2020 will be characterized by [19]:

Increased production efficiency with faster penetration rates allow for a greater

number of exploration and production drill holes.

Increased safety and efficiency with line-advancing or zero casing systems for

drill holes.

Lower costs and environmental impacts with In-situ extraction and processing

equipment.

Increased efficiency and production with sensing and imaging technologies

create smart drilling systems.

Smaller equipment and rigs, alternative to lubricants, or equipment that does

not need lubricants.

33

CHAPTER 3

3 STEPS OF THE EXPERIMENTAL WORK AND PROCEDURES

This chapter gives a brief description of the experimental procedures and

drilling data, according to the following general program of experimental work as

shown in Figure 3.1.

Cutter Type Rock Type Rotary Speed, WOB, Rock Drilling

(RPM) Kg properties result

Figure ‎3.1: Program of the experimental work

New

Diamond Bit

Mankabad

Limestone

Used

Diamond Bit

Minia

Limestone

Assiut

Limestone

Issawyia

Limestone

Zaraby

Limestone

Black Marble

White Marble

Pink Granite

Black

Granite

300

RPM

1000

RPM

15

Kg

30

Kg

45

Kg

60

Kg

390

Kg

480

Kg

570

Kg

ρ

gm/cm3

Р

%

бc

MPa

бt

MPa

бsh

MPa

μ

ROP

Cm/min.

SE

MPa

T

N.m

UCS/SE

MPa

34

Where:

The experimental work of the present investigation consists of two parts:

1. The first part is the determination of rock properties and the relation between

these properties and the penetration rate of the rock.

2. The second part is the drilling operations of the rock and how they are affected

by drilling conditions such as thrust acting on the rock, rotational speed of the

drill and bit conditions. ROP, SE, T and UCS/SE are the most important

parameters affecting the drilling operation. They are taken into consideration in

this thesis as a tool to predict the type of drilled rock.

3.1 Rock properties

Samples of rocks were collected from different localities as shown in location

map, Figure 1.1. Sedimentary, metamorphic, and igneous rocks are chosen for this

study. Sedimentary rocks are represented by five samples of limestone from three

different localities: the first type of limestone formation is from Assiut cement

company quarry, the second type is from Beni-Khaled, Minia, the third type is from

Mankabad quarry, north Assiut, the fourth type is from Zaraby quarry, the last type is

from Issawyia, east Sohag. Metamorphic rocks are represented by two types, White

and Black marbles are from Wadi-El-Miah, Eastern Desert. Igneous rocks are

WOB Specific weight on bit, Kg

ρ Density, gm/cm3

% P Porosity

Compressive strength, Mpa

Tensile strength, MPa

Shear strength, Mpa

μ Coefficient of internal friction

ROP Rate of penetration, cm/min.

SE Specific energy, MPa

T Torque, N.m.

⁄ Uniaxial compressive strength / Specific energy

35

represented by two types, Pink and Black granites are from Wadi- Allaqi, Aswan.

Selection of rock types was planned to meet the conditions upon which the results can

be discussed. Blocks about 20x15x10cm sizes formed by diamond saw from each type

of rock for the drilling tests. The most important physical and mechanical properties

of the tested rocks such as density, porosity, compressive strength, tensile strength, and

coefficient of internal friction‎ (μ)‎were‎ determined.‎ ‎ Table‎ 3.1 contains the average

value for each respective test together with its standard deviation.

Table ‎3.1: Physical and mechanical properties of the tested rocks

3.2 Drilling operations

In this study, blocks measuring 20x15x10 cm are formed by diamond saw from

each type of rock for the drilling tests. Diamond core drilling is applied for the tests.

The coring bits used have thin walled impregnated diamond type, the used bit has

inner diameter 40 mm and outer diameter 45 mm, the produced cores measure about

38 mm.

The load on the bit is applied by using hanging weights fixed on a movable

wheel by wire rope. The wheel is fixed on to the machine gear axis. Hence, the load

is transferred onto the bit. This transfer load is checked up and calibrated using

proving ring. Because of the important effect of load on the drilling operations,

drilling tests have been conducted using different loads.

Rock

Type

Density

(

⁄ )

Porosity

%

Compressive

strength,

MPa

Tensile

Strength,

MPa

Shear

Strength,

MPa

Coefficient

of Friction,

(µ)

Mankabad Limestone 1.72±0.0096 24.31±0.44 6.34±0.193 1.79±0.049 0.64±0.02 0.675

Minia Limestone 1.85±0.006 24.04±0.44 9.19±0.283 3.88±0.119 2.56±0.20 0.435

Assiut Limestone 2.18±0.0115 19.89±0.524 12.23±0.707 5.004±0.25 8.62±0.59 0.499

Issawyia Limestone 2.19±0.0137 15±3.26 16.02±0.905 6.77±0.383 5.02±0.21 0.488

Zaraby Limestone 2.39±0.0132 14.44±0.452 27.05±1.23 7.48±0.56 9.52±0.56 0.649

Black Marble 2.70±0.025 3.17±0.088 40.55±0.424 8.47±0.15 13.86±0.92 0.869

White Marble 2.74±0.0038 1.41±0.178 51.33±0.174 9.05±0.70 10.5±0.87 0.9004

Pink Granite 2.82±0.0161 1.29±0.25 74.88±3.78 9.75±0.513 11.02±0.66 0.93

Black Granite 2.90±0.0127 1.16±0.043 95.35±6.68 12.38±0.482 13.25±1.23 0.97

36

Data and conditions of drilling experiments and rocks under test were recorded.

Applied load, actual speeds, length of borehole, and time of drilling are recorded as

results of drilling. These results are used to calculate the drilling rate and the average

drilling rate at specific load of the rock, which are influenced by geological

parameters, machine parameters, and operating parameters.

Three trials were carried out for a particular weight on bit (WOB). Selection of

the WOB ranges for the bit was made by applying minimum WOB where the bit was

just capable of drilling the rock and maximum WOB just below the point where the

drill‎ commenced‎ to‎ stall‎ or‎ showed‎ “distressed”‎ drilling.‎ ‎ Five‎ to‎ Seven WOB

increments for each rock were selected between these limits. All drilling trials were

carried out at 300 rpm and 1000 rpm motor speed. The drilling speed value was the

unloaded speed; however, the speed is reduced over a small range with increasing

torque.

The drilling machine was a drill press modified to permit different applied

thrust or axial load, as shown in Figure (3-2). The drill speed can be adjusted to be

300 and 1000 rpm, by changing the variable speed drive. To apply the required axial

thrust on the bit, the feeding handle was replaced by a wheel used as a lever arm

(400mm) for dead weights. The drilling tool used in this work was diamond bits 45

mm (4.5 cm) diameter. The bit was attached to the main spindle of the drill. For

cooling the bit and removing the cuttings, water was used as a flushing media. Water

passes through a ring at a rate at a rate of 8 ⁄ (Q = 2.4 S), where "S" is the gap

cross- sectional area in . This arrangement resulted in the application of an axial

force to the drill while permitting the weights to remain stationary, thus ensuring

constant force acting downwards on the drill. Figure 3.3 represents a schematic

representation of the drilling machine. With the help of a proving ring, it becomes

possible to determine the actual load acting on the bit. Because the speeds taken from

the drill counter are misleading, the actual rotational speed at any test condition was

determined by a speedometer to calibrate the speed of tests. Water is used as cooling

37

and flushing media. The flow rate of water into coring bit equals about 8 liters/minute

calculated simply as follows:

Q = 2.4 S, where S is the gap cross- sectional area in .

Figure ‎3.2: Diamond core drilling machine

38

Figure ‎3.3: Schematic representation of the drilling machine [11].

1

2

3

4

56

7

8

9

10

11

12

13

14

1- Drilling press motor.

2- Gears,.........etc.

3- Depth measuring vernier.

4- Spindle.

5- Micro-bit.

6- Cooling water.

7- Fixed angle support.

8- Table.

9- Base.

10- Load.

11- Specimen.

12- Lever arm for load.

13- Flexible rope.

14- Free wheel to rotate

with hand.

39

3.3 Experimental data of drilling tests

The experimental data of operating parameters are presented in the following

Tables 3.2 to 3.15.

Table ‎3.2: Data of the drilling parameters in Mankabad limestone, Assiut

Weight

On bit,

Kg.

V1 = 300 rpm V2 = 1000 rpm

New bit Used bit New bit Used bit

Torque,

N.m

ROP,

cm/min.

Es,

MPa

Torque

N.m

ROP,

cm/min

Es,

MPa

Torque

N.m

ROP,

cm/min.

Es,

MPa

Torque

N.m

ROP,

cm/min

Es,

MPa

15 2.20 2.10 124.20 2.11 1.35 185.3 2.20 4.02 216.4 2.11 2.30 360.7

30 4.30 4.36 116.90 4.21 2.79 178.8 4.30 8.36 203.2 4.21 4.72 351.5

45 6.50 7.05 109.30 6.32 4.24 176.8 6.50 13.18 194.9 6.32 7.39 336.8

60 8.60 9.83 103.70 8.42 5.85 170.5 8.60 19.53 174 8.42 10.18 326.0

75 10.80 2.7 0 474.10 10.53 2.63 473.2 10.80 7.21 519.8 10.53 6.53 635.2

Table ‎3.3: Data of the drilling parameters in Beni-Khalid- Samalout limestone, Minia

Weight

On bit,

Kg.

V1 = 300 rpm V2 = 1000 rpm


Torque,

N.m

ROP,

cm/min.

Es,

MPa

Torque

N.m

ROP,

cm/min

Es,

MPa

Torque

N.m

ROP,

cm/min.

Es,

MPa

Torque

N.m

ROP,

cm/min

Es,

MPa

15 1.4 0.76 218.32 1.4 0.63 263.4 1.4 1.65 335.2 1.4 1.23 677.7

30 2.8 2.14 155.07 2.7 1.36 235.3 2.8 4.42 250.3 2.7 2.75 387.9

45 4.2 3.92 126.98 4.1 2.19 221.9 4.2 6.85 242.2 4.1 4.52 358.4

60 5.6 6.11 108.63 5.4 2.93 218.4 5.6 9.53 232.1 5.4 6.13 348.0

75 6.9 7.92 103.25 6.8 4.13 195.2 6.9 13.16 207.1 6.8 8.2 327.6

90 8.3 10.21 96.35 8.1 5.37 178.7 8.3 16.32 200.9 8.1 10.92 293.0

105 9.7 12.16 94.54 9.5 7.3 154.3 9.7 13.67 280.33 9.5 8.65 433.9

120 11.1 6.47 203.33 10.9 4.17 309.8 11.1 - - 10.9 - -

40

Table ‎3.4: Data of the drilling parameters in Assiut cement company quarry limestone, Assiut

Weight

On bit,

Kg.

V1 = 300 rpm V2 = 1000 rpm


Torque,

N.m

ROP,

cm/min.

Es,

MPa

Torque

N.m

ROP,

cm/min

Es,

MPa

Torque

N.m

ROP,

cm/min.

Es,

MPa

Torque

N.m

ROP,

cm/min

Es,

MPa

15 1.60 0.64 296.30 1.60 0.52 364.7 1.60 1.08 585.3 1.60 0.7 902.7

30 3.20 1.92 197.50 3.10 1.08 340.2 3.20 2.53 499.7 3.10 2.11 580.4

45 4.80 3.24 175.60 4.70 1.73 322.0 4.80 4.27 444.1 4.70 3.68 504.6

60 6.40 5.33 142.30 6.20 2.75 267.2 6.40 6.12 413.1 6.20 5.56 440.5

75 8.00 7.00 135.40 7.80 3.86 239.5 8.00 8.80 359.1 7.80 7.61 404.9

90 9.50 9.53 118.10 9.30 5.21 211.6 9.50 11.25 333.6 9.30 10.14 362.3

105 11.10 2.71 485.40 10.90 2.42 533.8 11.10 6.78 646.8 10.90 5.29 814.0

Table ‎3.5: Data of the drilling parameters in Issawyia limestone, east Sohag

Weight

On bit,

Kg.

V1 = 300 rpm V2 = 1000 rpm


Torque,

N.m

ROP,

cm/min.

Es,

MPa

Torque

N.m

ROP,

cm/min

Es,

MPa

Torque

N.m

ROP,

cm/min.

Es,

MPa

Torque

N.m

ROP,

cm/min

Es,

MPa

15 1.60 0.58 327.0 1.50 0.46 386.5 1.60 0.98 645.0 1.50 0.62 955.8

30 3.10 1.42 258.7 3.00 1.00 355.6 3.10 2.37 516.7 3.00 1.97 601.6

45 4.70 2.52 221.0 4.60 1.62 336.5 4.70 4.98 372.8 4.60 3.13 580.6

60 6.20 3.63 202.4 6.10 2.62 275.5 6.20 8.19 299.1 6.10 5.21 462.5

75 7.80 4.73 195.4 7.60 3.77 238.7 7.80 10.83 284.5 7.60 7.18 418.2

90 9.30 6.60 167.0 9.10 4.87 221.5 9.30 13.32 275.8 9.10 9.68 371.4

105 10.90 3.50 369.1 10.70 2.42 524.0 10.90 5.50 782.9 10.70 4.62 915.0

41

Table ‎3.6: Data of the drilling parameters in Zaraby limestone, Assiut

Weight

On bit,

Kg.

V1 = 300 rpm V2 = 1000 rpm


Torque,

N.m

ROP,

cm/min.

Es,

Mpa

Torque

N.m

ROP,

cm/min

Es,

Mpa

Torque

N.m

ROP,

cm/min.

Es,

Mpa

Torque

N.m

ROP,

cm/min

Es,

Mpa

15 2.10 0.47 529.5 2.02 0.40 598.5 2.10 0.93 892.0 2.02 0.60 1330

30 4.10 0.98 495.8 4.05 0.87 551.7 4.10 2.30 704.2 4.05 1.76 909.1

45 6.20 1.67 440.0 6.07 1.44 494.6 6.20 3.58 684.2 6.07 2.83 847.4

60 8.30 2.52 390.3 8.10 2.12 452.8 8.30 5.16 635.4 8.10 4.71 679.4

75 10.40 3.37 365.7 10.12 2.85 420.8 10.40 7.54 544.9 10.12 6.92 577.7

90 12.40 4.22 348.2 12.15 3.67 392.4 12.40 11.26 435.0 12.15 9.13 525.7

120 14.50 2.96 664.6 16.20 2.15 893.0 14.50 4.97 1153 16.20 4.11 1154

Table ‎3.7: Data of the drilling parameters in Black marble, Wadi El-Miah, Eastern Desert

Weight

On bit,

Kg.

V1 = 300 rpm V2 = 1000 rpm


Torque,

N.m

ROP,

cm/min.

Es,

MPa

Torque

N.m

ROP,

cm/min

Es,

MPa

Torque

N.m

ROP,

cm/min.

Es,

MPa

Torque

N.m

ROP,

cm/min

Es,

MPa

30 5.50 0.79 825.13 5.40 0.62 1033 5.50 2.02 1077 5.40 0.92 2319

45 8.30 1.55 634.65 8.10 1.25 768.0 8.30 3.50 936.9 8.10 1.86 1720

60 11.10 2.37 555.09 10.80 2.00 640.0 11.10 4.95 885.9 10.80 2.61 1635

75 13.90 3.25 506.89 13.60 2.77 581.9 13.90 7.33 749.2 13.60 5.10 1054

90 16.60 4.11 478.69 16.30 3.56 542.7 16.60 10.33 634.9 16.30 6.86 937.3

105 19.40 2.38 966.08 19.00 1.97 1143 19.40 5.40 1419 19.00 3.39 2214

42

Table ‎3.8: Data of the drilling parameters in White marble, Wadi El-Miah, Eastern Desert

Weight

On bit,

Kg.

V1 = 300 rpm V2 = 1000 rpm


Torque,

N.m

ROP,

cm/min.

Es,

MPa

Torque

N.m

ROP,

cm/min

Es,

MPa

Torque

N.m

ROP,

cm/min.

Es,

MPa

Torque

N.m

ROP,

cm/min

Es,

MPa

30 5.70 0.68 993.5 5.60 0.57 1164 5.70 1.43 1575 5.60 0.81 2731

45 8.60 1.15 886.31 8.40 1.05 948.2 8.60 2.68 1267 8.40 1.70 1952

60 11.50 2.24 608.47 11.20 1.54 862 11.50 4.28 1062 11.20 2.53 1749

75 14.40 3.12 547.01 14.00 2.09 793.9 14.40 6.18 920.5 14.00 4.42 1251

90 17.20 4.00 509.63 16.90 2.76 725.7 17.20 7.66 887.1 16.90 5.78 1155

105 20.11 1.86 1281.4 19.70 1.83 1276 20.11 5.32 1493 19.70 3.20 2432

Table ‎3.9: Data of the drilling parameters in Pink granite, Aswan

Weight

On bit,

Kg.

V1 = 300 rpm V2 = 1000 rpm


Torque,

N.m

ROP,

cm/min.

Es,

MPa

Torque

N.m

ROP,

cm/min

Es,

MPa

Torque

N.m

ROP,

cm/min.

Es,

MPa

Torque

N.m

ROP,

cm/min

Es,

MPa

90 22 0.4 5277.0 21.5 0.3 6874.2 22 0.9 7817.8 21.5 0.45 15275.7

120 29.4 0.71 3962.9 28.7 0.43 6394.6 29.4 1.35 6947.2 28.7 0.75 12220.5

150 36.7 1.06 3318.6 35.9 0.56 6137.6 36.7 1.78 6587.3 35.9 1.2 9547.3

180 44.1 1.51 2795.0 43.1 0.79 5220.9 44.1 2.35 5986.4 43.1 2.11 6515.7

210 51.4 2.09 2914.7 50.2 1.002 4802.3 51.4 3.14 5227.6 50.2 2.48 6467.5

240 58.7 1.65 3410.5 57.4 0.57 9647.9 58.7 1.88 9977.4 57.4 1.77 10356.4

43

Table ‎3.10: Data of the drilling parameters in Black granite, Aswan

Weight

On bit,

Kg.

V1 = 300 rpm V2 = 1000 rpm


Torque,

N.m

ROP,

cm/min.

Es,

MPa

Torque

N.m

ROP,

cm/min

Es,

MPa

Torque

N.m

ROP,

cm/min.

Es,

MPa

Torque

N.m

ROP,

cm/min

Es,

MPa

90 - - - - - - 22.80 0.70 12867 22.30 0.30 29366

120 30.40 0.44 8188.3 29.70 0.34 10304 30.40 1.02 11774 29.70 0.63 18624

150 - - - - - - 38.00 1.42 10572 37.20 0.94 15699

180 - - - - - - 45.60 1.84 9790 44.60 1.43 12304

210 53.20 1.33 4740.6 52.10 0.78 7959 53.20 2.39 8794 52.10 1.77 11603

240 - - - - - - 60.80 2.89 8311 59.50 2.40 9794

270 - - - - - - 68.50 1.30 20816 66.90 1.12 23598

300 76.10 2.48 3636.7 74.40 1.20 7348 - - - - - -

390 98.90 3.43 3417.2 96.70 1.82 6297 - - - - - -

480 121.7 4.80 3004.8 119.0 2.63 5363 - - - - - -

570 144.5 2.60 6586.7 141.3 1.67 10028 - - - - - -

44

Table ‎3.11: Specific energy and UCS/SE for limestone at 300, and 1000 rpm and different

loads, new bit

WOB,

Kg

UCS,

MPa

SE, MPa (UCS/SE) ROP, ⁄

300 rpm 1000 rpm 300 rpm 1000 rpm 300 rpm 1000 rpm

15

6.34 124.2 216.4 51.05 29.3 21 40.2

9.19 218.32 335.2 42.09 27.42 7.6 16.5

12.23 296.3 585.28 41.28 20.90 6.4 10.8

16.02 326.95 645 49 24.84 5.8 9.8

27.05 529.5 892 51.09 30.33 4.7 9.3

30

6.34 116.9 203.2 54.23 31.2 43.6 86.3

9.19 155.07 250.3 59.26 36.7 21.4 44.2

12.23 197.5 499.7 61.92 24.47 19.2 25.3

16.02 258.7 516.7 61.93 31 14.2 23.7

27.05 495.8 704.2 54.56 38.41 9.8 23

45

6.34 109.3 194.9 58.01 32.52 70.5 131.8

9.19 126.98 242.2 72.37 37.94 39.2 68.5

12.23 175.6 444.1 69.65 27.54 32.4 42.7

16.02 221 372.8 72.49 42.97 25.2 49.8

27.05 440 684.2 61.48 39.54 16.7 35.8

60

6.34 103.7 174 61.14 36.44 98.3 195.3

9.19 108.63 232.1 84.6 39.6 61.1 95.3

12.23 175.6 413.1 69.65 29.61 32.4 61.2

16.02 202.4 299.1 72.49 53.56 36.3 81.9

27.05 390.3 635.4 61.48 42.57 25.2 51.6

75

9.19 103.25 207.1 89.01 44.37 79.2 131.6

12.23 135.4 359.1 90.32 34.06 70 88

16.02 95.4 284.5 81.99 56.31 47.3 108.3

27.05 365.7 544.9 73.97 49.64 33.7 75.4

90

9.19 96.35 200.9 95.38 45.74 102.1 163.2

12.23 118.1 333.6 103.56 36.66 95.3 112.5

16.02 167 275.8 95.93 58.09 66 133.2

27.05 348.2 435 77.69 62.18 42.2 112.6

45

Table ‎3.12: Specific energy and UCS/SE for Marbles at 300, and 1000 rpm and different

loads, new bit

WOB,

Kg

UCS,

MPa

SE,

MPa (UCS/SE)

ROP,

mm/min.

300

rpm

1000

rpm

300

rpm

1000

rpm

300

rpm

1000

rpm

30 40.55 825.13 1077.4 49.14 37.6 7.9 20.2

51.33 993.46 1574.72 51.67 32.6 6.8 14.3

45 40.55 634.65 936.86 63.89 43.3 15.5 35

51.33 886.31 1266.76 57.91 40.5 11.5 26.8

60 40.55 555.09 885.9 73.05 45.8 23.7 49.5

51.33 608.47 1061.49 84.36 48.4 22.4 42.8

75 40.55 506.89 749.16 80 54.1 32.5 73.3

51.33 547.01 920.53 93.84 55.8 31.2 61.8

90 40.55 478.69 634.85 84.71 63.9 41.1 103

51.33 509.63 887.08 100.7 57.9 40 76.6

Table ‎3.13: Specific energy and UCS/SE for Granites at 300, and 1000 rpm and different

loads, new bit

WOB,

Kg

UCS,

MPa

SE,

MPa (UCS/SE)

ROP,

mm/min.

300

rpm

1000

rpm

300

rpm

1000

rpm

300

rpm

1000

rpm

90 74.88 6518.3 9656.8 11.5 7.75 4 9

95.35 - 12867.3 - 7.41 - 7

120 74.88 4907.5 8603.3 15.3 8.7 7.1 13.5

95.35 8188.3 1174 11.6 8.1 4.4 10.2

150 74.88 4103.3 8145.1 18.3 9.19 10.6 17.8

95.35 - 10571.8 - 9.02 - 14.2

180 74.88 3461.3 7402.9 21.6 10.11 15.1 23.5

95.35 - 9790.4 - 9.74 - 18.4

210 74.88 2914.7 6466.8 25.7 11.58 20.9 31.9

95.35 4740.6 8793.6 20.1 10.84 13.3 23.9

300 74.88 - - - - - -

95.35 3636.7 - 26.2 - 24.8 -

390 74.88 - - - - - -

95.35 3417.2 - 27.9 - 34.3 -

480 74.88 - - - - - -

95.35 3004.8 - 31.7 - 48 -

46


rpm at different loads (WOB)

Weight

On bit,

Kg.

Limestone Marbles Granites

ROP,

mm/min.

SE,

Mpa

ROP,

mm/min.

SE,

MPa

ROP,

mm/min.

SE,

MPa

15 17.32 534.78 - - - -

30 40.50 434.82 17.25 1326.06 - -

45 65.72 387.64 30.9 1101.81 - -

60 97.06 350.74 46.15 973.7 - -

75 100.83 348.9 67.55 834.85 - -

90 130.38 311.33 89.95 760.97 8 11262.05

120 - - - - 11.85 10188.65

150 - - - - 16 9358.45

180 - - - - 20.95 8596.65

210 - - - - 27.65 7630.20


rpm at different loads (WOB)

Weight

On bit,

Kg.

limestone Marbles Granites

ROP,

mm/min.

SE,

Mpa

ROP,

mm/min.

SE,

MPa

ROP,

mm/min.

SE,

MPa

15 9.1 299.05 - - - -

30 21.64 244.79 7.35 909.3 - -

45 36.8 214.58 13.5 760.48 - -

60 50.66 196.13 23.05 581.78 - -

75 65.5 144.68 31.85 526.95 - -

90 87.80 127.15 40.55 494.16 4 6518.3

120 - - - - 5.75 6547.9

150 - - - - 10.6 4103.3

180 - - - - 15.1 3461.3

210 - - - - 17.1 3827.65

300 - - - - 24.8 3636.7

390 - - - - 34.3 3417.2

480 - - - - 48 3004.8

47

CHAPTER 4

4 RESULTS AND DISCUSSIONS

In this chapter the effects of both weight on bit (WOB), rotary speed (RPM), bit

conditions on rate of penetration (ROP), and new drilling index (UCS/SE) were

discussed:

4.1 Effect of both weight on bit, rotary speed, and bit condition on rate of penetration

The effect of weight on bit (WOB) on the rate of penetration (ROP) is given in

Tables 3.2 to 3.10 and Figures 4.1 to 4.9. From these results it is clear that, the

increasing of the weight on bit (WOB) produces an increase in the rate of penetration

(ROP) up to a maximum point. However, a further increase in weight on bit (WOB)

causes little increase, or even a decrease in the rate of penetration (ROP) in all types of

tested rocks.

Figure ‎4.1: Relation between weight on bit (WOB) and rate of penetration (ROP) at

300 and 1000 rpm in Mankabad limestone, Assiut

0

5

10

15

20

25

10 20 30 40 50 60 70 80

Rat

e o

f p

enet

rati

on (

RO

P),

cm

/min

.

Weight on bit (WOB), kg

V1 =300 rpm (New bit)

V1=300 rpm (Used bit)

V2= 1000 rpm (New bit)


48

Figure ‎4.2: Relation between weight on bit and rate of penetration at 300 and 1000

rpm in Beni Khalid- Samalout limestone, Minia


rpm in Assiut limestone

0

2

4

6

8

10

12

14

16

18

0 20 40 60 80 100 120 140

Rat

e o

f p

enet

rati

on (

RO

P),

cm

/min

.

Weight on bit (WOB), Kg





0

2

4

6

8

10

12

0 20 40 60 80 100 120

Rat

e o

f p

enet

rati

on (

RO

P),

cm

/min

.






49


rpm in Issawyia limestone, East Sohag


rpm in Zaraby limestone, Assiut

0

2

4

6

8

10

12

14

0 20 40 60 80 100 120

Rat

e o

f p

enet

rati

on (

RO

P),

cm

/min

.




0

2

4

6

8

10

12

0 20 40 60 80 100 120

Rat

e of

pen

etra

tion (

RO

P),

cm

/min

.






50


rpm in Black marble, Wadi El-Miah


rpm in white marble, Wadi El-Miah

0

1

2

3

4

5

6

7

8

9

20 40 60 80 100 120

Rat

e o

f p

enet

rati

on (

RO

P),

cm

/min

.






0

2

4

6

8

10

12

20 40 60 80 100 120

Rat

e o

f p

enet

rati

on (

RO

P),

cm

/min

.






51


rpm in pink granite, Aswan


rpm in Black granite, Aswan

0

0.5

1

1.5

2

2.5

3

3.5

70 90 110 130 150 170 190 210 230 250

Rat

e o

f p

enet

rati

on (

RO

P),

cm

/min

.






0

1

2

3

4

5

6

0 100 200 300 400 500 600

Rat

e o

f p

enet

rati

on (

RO

P),

cm

/min

.






52

Tables 4.1 & 4.2 give correlation equations of the relationship between rate of

penetration (ROP) and weight on bit (WOB) for all tested rocks at 300 rpm and

1000 rpm respectively.

Table ‎4.1: Correlation equations of the relationship between rate of penetration and

the weight on bit for all tested rocks at 300 rpm

Rock

type

New bit

*R

Used bit

*R

Mankabad

limestone

ROP= -0.0059 WOB2

+0.5785

WOB – 6.138

0.84

ROP= -0.0029 WOB2

+ 0.2992

WOB -2.894

0.88

Minia

limestone

ROP= -0.0013 WOB2

+0.258

WOB – 3.9745

0.90

ROP= -0.0004WOB2

+0.1079

WOB – 1.3875

0.89

Assiut

limestone

ROP= -0.0019WOB2

+0.284

WOB – 4.3014

0.80

ROP= -0.0007 WOB2

+0.1213

WOB – 1.6557

0.84

Issawyia

limestone

ROP= -0.0008WOB2

+0.1515

WOB – 2.0314

0.88

ROP= -0.0006WOB2

+0.1153

WOB – 1.6086

0.91

Zaraby

limestone

ROP= -0.0004WOB2

+ 0.0906

WOB – 1.0729

0.94

ROP= -0.0005WOB2

+ 0.095

WOB – 1.0514

0.90

White

marble

ROP= 0.0013 WOB2

+

0.208WOB – 4.0953

0.86

ROP= -0.0005WOB2

+

0.0928WOB – 1.8596

0.91

Black

marble

ROP= -0.001 WOB2

+0.1631

WOB – 3.5184

0.90

ROP= -0.0009WOB2

+ 0.1447

WOB – 5.9544

0.83

Pink

granite

ROP= -6 -5 (WOB2 )

+ 0.0289

WOB – 3.849

0.94

ROP= -5 -5 (WOB2)

+ 0.0194 WOB

– 3.124

0.84

Black

granite

ROP= -3 -5 (WOB)2

+ 0.0292

WOB – 2.978

0.90

ROP= -1-5 (WOB)2

+ 0.0123 WOB

-1.1416

0.90

53

Table ‎4.2: Correlation equations of the relationship between rate of penetration and the weight on

bit for all tested rocks at 1000 rpm

Rock

type

New bit

*R

Used bit

*R

Mankabad

limestone

ROP= -0.0101 WOB2

+ 1.0253

WOB – 10.7

0.84

ROP= -0.0038 WOB2

+ 0.4362

WOB – 3.962

0.92

Minia

limestone

ROP=-0.0011 WOB2 + 0.2944

WOB - 3.16

0.97

ROP=-0.0007 WOB2 + 0.185

WOB – 1.88

0.96

Assiut

limestone

ROP=-0.0013 WOB2 + 0.2479

WOB - 3.2329

0.91

ROP=-.0014 WOB2 + 0.2465

WOB – 3.5471

0.88

Issawyia

limestone

ROP=-0.0025 WOB2 + 0.4018

WOB –6.1329

0.86

ROP=-0.0014WOB2 +

0.2373WOB-3.5186

0.86

Zaraby

limestone

ROP=-0.0013 WOB2 + 0.2365

WOB – 0.625

0.82

ROP=-0.0013 WOB2 + 0.2257

WOB –1.403

0.85

White

Marble

ROP= -0.0015 WOB2

+ 0.2765

WOB -5.7787

0.93

ROP= -0.0012WOB2

+ 0.2129

WOB –3.991

0.87

Black

Marble

ROP=-0.0021 WOB2 + 0.3527

WOB –7.5261

0.84

ROP=-0.0014WOB2 + 0.2498

WOB -5.9544

0.83

Pink

Granite

ROP=-0.0001 WOB2 + 0.0509

WOB –3.2738

0.86

ROP=-.0001 WOB2 + 0.0486

WOB – 3.496

0.92

Black

Granite

ROP = 1.39 ln (WOB) – 5.50

0.70

ROP = 1.43 ln (WOB) – 6.09

0.79

*R: Correlation coefficient

As shown in Figures 4.1 to 4.9, limestone, marble, and granite need 15, 30,

and 90 kg as a minimum load to begin drilling respectively. The best load (WOB) is

the weight which gives maximum value of the penetration rate (ROP) and minimum

value of specific energy for rock drilling. From Figure 4.1 for Mankabad limestone,

the best weight on bit is 60 kg, that gives maximum value of rate of penetration

(ROP=4.6 cm/min.) at 300 rpm when using used bit, and (ROP=7.3 cm/min.) when

54

using new bit at the same rotary speed 300 rpm. And the rate of penetration at 1000

rpm for used bit is (ROP= 8.50 cm/min.) and is (ROP=14.50 cm/min.) with new bit at

1000 rpm.

Figure 4.2 shows that the best weight on bit required for drilling in Minia

limestone is (WOB= 105 kg) at 300 rpm which gives the highest rate of penetration

value (ROP= 5.6 cm/min.) for used bit and is (ROP= 9.2 cm/min.) for new bit at the

same rotational speed 300 rpm. When the drilling speed increases to 1000 rpm, and at

best weight (90 kg WOB) the rate of penetration is (ROP= 9.4 cm/min.) with used bit

and is (ROP = 13.6 cm/min.) with new bit .

Figure 4.3, gives the best weight on bit during drilling in Assiut limestone is 90

kg WOB, which gives (ROP = 3.6 cm/min.) for used bit and (ROP= 6.4 cm/min.) for

new bit both are at 300 rpm., but when the drilling speed is 1000 rpm the rate of

penetration for used and new bit respectively is 7.6 cm/min. & 8.6 cm/min.

Figure 4.4, shows the best load on bit wanted in drilling in Issawyia limestone

is 90 kg WOB, that gives maximum value of the penetration rate (ROP= 3.6 cm/min.)

for used bit and is (ROP= 4.87 cm/min.) for new bit both are at 300 rpm. When the

drilling speed becomes 1000 rpm the drilling rate is (ROP= 6.8 cm/min.) for used bit

and (ROP=9.68 cm/min.) for new bit.

Figure 4.5 shows the best load on bit for Zaraby limestone is 90 kg WOB,

which produces maximum value of penetration rate (ROP= 2.8 cm/min.) for used bit

and (ROP= 3.47 cm/min.) for new bit both are at 300 rpm, and when the drilling speed

is 1000 rpm the rate of penetration is (ROP= 6.4 cm/min.) for used bit and (ROP= 7.6

cm/min.) for new bit.

From these results and figures of all limestone rocks, we found that the

maximum value of rate of penetration at 60 kg WOB is in Mankabad limestone and

the minimum value is in Zaraby limestone at the same conditions (bit conditions,

drilling speed and WOB).

55

Rate of penetration at 60 kg WOB in Mankabad limestone is (1.61-2.05) times

than that in Minia limestone, and is (1.83-3.19) times than that of Assiut limestone,

and is (1.95-2.71) times than that of Issawyia limestone, and is (2.16-3.90) times than

that of Zaraby limestone, at both new and used bit for two different rotary speeds 300

&1000 rpm. This related to Zaraby limestone is most hard than all these tested

limestone.

Figure 4.6 & 4.7 show that the minimum load of 90 kg is required to begin

drilling in Black and White marble respectively. In Black marble at 90 kg WOB the

rate of penetration is (ROP= 1.03-1.35) times than that of White marble at 300 and

1000 rpm and for both used and new bit.

Figures 4.8 & 4.9 illustrate that the minimum load of 90 kg is required to begin

drilling in pink and black granite respectively. For pink granite, the best load on bit is

210 kg WOB (Fig.4.8) that gives rate of penetration (ROP= 0.75 cm/min.) for new bit

and (ROP= 1.8 cm/min.) for used bit both at 300 rpm, but at 1000 rpm the rate of

penetration is (ROP= 2.09 cm/min.) for new bit and is (ROP=2.48 cm/min.) for used

bit.

For black granite as shown in Figure 4.9, the best load of 480 kg is required to

give maximum value of penetration rate (ROP=4.8 cm/min.) for new bit and

(ROP=2.63 cm/min.) for used bit at 300 rpm. And the best load of 240 kg is required

to give maximum value of penetration rate (ROP=2.40 cm/min.) for used bit and (ROP

=2.8 cm/min.) for new bit at 1000 rpm. By comparing three categories of rocks, we

found that all figures illustrate that the highest value of penetration rate was obtained

during drilling in limestone by using small loads on bit than marbles and granites,

because the granites are most hard than marbles and limestone.

To show the effect of bit conditions on the rate of penetration (ROP), drilling

machine was set at nominal speeds at 300 and 1000 rpm for all the tests. For

Mankabad limestone, as shown in Fig. 4.1, the rate of penetration at 60 kg using new

bit is (1.68 -1.92) times at 300 and 1000 rpm than that using used bit respectively.

56

For Minia limestone, Fig. 4.2, gives the rate of penetration at 105 kg, using

new bit is (1.67) times than that at using bit at 300 rpm, and the rate of penetration at

90 kg at 1000 rpm when using new bit is (1.50) times than with used bit . For Assiut

limestone Fig. 4.3, gives the rate of penetration at 90 kg is (1.11-1.83) times at 300 and

1000 rpm than with used bit respectively.

For Issawyia limestone, Fig. 4.4 gives the rate of penetration at 90 kg, at 300

and 1000 rpm is (1.36-1.38) times than with using bit. For Zaraby limestone, Fig. 4.5,

gives the rate of penetration at 90 kg at 300 and 1000 rpm is (1.15-1.23) times that

when using used bit respectively.

For black marble, Fig. 4.6, the rate of penetration at 90 kg at 300 and 1000 rpm

is (1.15-1.51) times than with used bit respectively. For white marble, Fig. 4.7, the

rate of penetration at 90 kg at 300 and 1000 rpm is (1.33-1.45) times than with used bit

respectively.

For pink granite, Fig. 4.8, the rate of penetration at 210 kg at 300 and 1000 rpm

is (2.09-1.27) times than when using used bit respectively. For black granite, Fig. 4.9,

the rate of penetration at 480 kg at 300 rpm is (1.82) times than with used bit, and the

rate of penetration at 210 kg at 1000 rpm is (1.20) times than that with used bit.

4.2 Effect of both weight on bit, rotary speed and bit conditions on torque

The torque is a measure of resistive forces opposing rotation and is a function

of friction, cutting or shearing forces and abrasion at the bit/rock interface. Hence

with increasing WOB the friction resistance is increased and required greater torque,

being dependent upon the strength of the rock. For diamond drilling coring bit, the

normal pressure (WOB) can be assumed to be uniform over drilled annulus. Thus the

resisting torque over the total area of the annulus determined by [39, 47].

⁄

(‎4.1)

57

Where,

T = resisting torque, kgfm

Fv = applied thrust, kgf.

ro = outside radius, m

ri = inside radius, m

= Coefficient of friction

There is a linear relation between the two parameters (WOB & T) up to the

critical value or stalling conditions, the rate of penetration rises with increasing weight

on bit WOB at both two drilling speeds 300 and 1000 rpm for both two bit conditions.

Figures 4.10 & 4.11 show the relations between weight on bit (WOB) and torque (T),

one type from the three rock categories is given as an example representing constant

drilling speed and different bit conditions.

Figure ‎4.10: Relation between weight on bit and torque at 300 rpm using new bit, For

Zaraby limestone (Assiut), white (Wadi El-Miah Eastern Desert), and pink

granite (Aswan)

0

10

20

30

40

50

60

70

0 50 100 150 200 250 300

Torq

ue

(T),

N.m


Zaraby Limestone

White Marble

Pink Granite

58

Figure ‎4.11: Relation between weight on bit and torque at 300 rpm using used bit, For

Zaraby limestone (Assiut), white marble (Wadi El-Miah Eastern Desert),

and pink granite (Aswan)

Table ‎4.3: Correlation equations of the relationship between Torque (T) and weight on bit

(WOB) at 300 rpm


4.3 Effect of weight on bit, rotary speed, and bit condition on specific energy

The drilling specific energy is very significant measure of drilling performance.

It is directly compatible with cost/meter, because it relates to the amount of energy

required to penetrate rock. Specific energy (SE) can also be used to quantify the

efficiency of rock working processes and to indicate bit conditions, rock strength and

rock hardness during drilling [56]. It is considered a good indication to judge the bit

performance and how it behaves in a particular rock. Specific energy can be defined,

0

10

20

30

40

50

60

70

0 50 100 150 200 250 300

To

rqu

e (T

), N

.m


Zaraby Limestone

White Marble

Pink Granite

Rock type New bit *R

Used bit *R

Zaraby limestone T = 0.1228 WOB + 0.6537 0.99 T = 0.135 WOB – 0.0042 0.99

White Marble T= 0.1919 WOB -0.0352 0.99 T = 0.1882WOB - 0.0695 0.99

Pink Granite T = 0.2447 WOB +0.0133 0.99 T = 0.2392 WOB -0.0076 0.99

59

as the energy required for removing a unit volume of rock, or as the quantity of the

energy from a source expended through the bit to drill a volume of rock. It is a

variable of drilling process that is dependent on all the main drilling parameters:

weight on bit, rotational speed, penetration rate and the strength of rock. For example,

the specific energy serves to give an indication of the efficiency of the drilling process.

It is easily calculated for rotary drilling by means of the equation [4, 57, 58, 59, 68].

(‎4.2)

Where:

SE = Specific energy, Mpa

N = rotary speed, rpm

T = resistance torque, N.m

A = area of the bit, mm2

ROP= rate of penetration, m/hr

Figure 4.12 shows the relation between weight on bit (WOB) and specific

energy (SE) for Mankabad limestone at two different drilling speeds 300 and 1000

rpm. It obvious from this figure that the, specific energy decreases as weight on bit

increases until 60 kg WOB. So, this value is the best weight on bit (WOB) for drilling

this type of rock Figure 4.12. Figure 4.13 shows also, the relation between weight on

bit (WOB) and specific energy (SE) in Minia limestone. At WOB of 105 kg and 300

rpm the minimum value of specific energy was obtained. However, at 1000 rpm the

minimum value of specific energy was obtained at 90 kg WOB. Figure 4.14 introduces

the relation between weight on bit (WOB) and specific energy (SE) in Assiut

limestone at 300 and 1000 rpm. The minimum value of the specific energy is obtained

at 90 kg WOB.

60

Figure ‎4.12: Relation between weight on bit and specific energy at 300 and 1000 rpm

in Mankabad limestone

Figure ‎4.13: Relation between weight on bit and Specific energy at 300 and 1000 rpm

in Beni-Khalid, Samalout Limestone, Minia

0

100

200

300

400

500

600

700

0 20 40 60 80 100 120 140

Spec

ific

ener

gy (

SE

), M

pa






0

100

200

300

400

500

600

700

10 20 30 40 50 60 70 80

Sp

ecif

ic e

ner

gy (

SE

), M

pa






61


in Assiut cement company quarry Limestone, Assiut


in Issawyia Limestone, East Sohag

0

100

200

300

400

500

600

700

800

900

1000

0 20 40 60 80 100 120

Spec

ific

ener

gy (

SE

), M

pa






0

200

400

600

800

1000

1200

0 20 40 60 80 100 120

Sp

ecif

ic e

ner

gy (

SE

), M

pa






62


in Zaraby Limestone, Assiut

Figures 4.15 & 4.16 show that, at 90 kg WOB, 300, and 1000 rpm in Issawyia

and Zaraby Limestone, the minimum value of specific energy was obtained with both

new and used bits. So, this value is the best weight on bit (WOB) for drilling these two

types of rocks Figures 4.15 & 4.16.

By comparing all limestone rocks, results revealed that the minimum amount of

energy needed for drilling was for Mankabad limestone, and the maximum value of

consumed energy required during drilling was for Zaraby limestone, because Zaraby is

hardest one of all tested limestone. While, the minimum value of consumed energy

required during drilling was for Mankabad limestone, because Mankabad is the

weakest one of all tested limestone.

Zaraby limestone consumed (1.42, 2.08) and (1.45, 2.95) times of specific

energy for being drilled than Issawyia, and Assiut limestone at 90 kg WOB, 300 and

1000 rpm, respectively for both new and used bit. While, the specific energy needed in

Zaraby limestone is a (1.79-3.61) time that wanted for drilling Minia limestone at 300

and 1000 rpm for new and used bit at 105 kg WOB.

0

200

400

600

800

1000

1200

1400

1600

0 20 40 60 80 100 120

Sp

ecif

ic e

ner

gy (

SE

), M

pa






63

Also the specific energy consumed for drilling Zaraby limestone is (2.08-3.76)

times that consumed during drilling Mankabad limestone at 60 kg. Figures 4.17& 4-18

show that the specific energy consumed for drilling black and white marble is higher

than that consumed in all limestone rocks at 300 and 1000 rpm and 90 kg weight on bit

(WOB).


in Black Marble, Wadi El-Miah, Eastern Desert


in White Marble, Wadi El-Miah, Eastern Desert

0

500

1000

1500

2000

2500

3000

0 20 40 60 80 100 120

Sp

ecif

ic e

ner

gy (

SE

), M

pa






0

500

1000

1500

2000

2500

3000

20 40 60 80 100 120

Sp

ecif

ic e

ner

gy (

SE

), M

pa






64

The specific energy consumed for black marble, at 90 kg, 300 and 1000 rpm is

(1.07-1.4) times that needed for drilling in white marble at the same values of WOB

and RPM. Also, the comparison between specific energy required for marbles and

limestone has shown that the specific energy for white marble was (1.5-2.2) times that

for Zaraby limestone which is the hardest limestone rock in our research.

Figures 4.19 & 4.20 for pink and black granites, illustrate that the specific

energy consumed in black granite at 210 kg and 300 and 1000 rpm for used and new

bit is (1.34-1.63) times that consumed in drilling pink granite.


in pink granite, Aswan

Bit condition has a great influence on the amount of specific energy consumed.

Using new bit at constant weight on bit of 90 kg WOB and rotary speed of 1000 rpm,

the specific energy consumed for drilling the black granites was 14.5, 29.6 times that

consumed in white marble and Zaraby limestone respectively. The amount of specific

energy was highly increased and became 25.42, 55.9 times that in white marble and

Zaraby limestone respectively.

0

5000

10000

15000

20000

25000

70 120 170 220 270

Spec

ific

ener

gy (

SE

), M

pa






65

The effect of rotary drilling speed on specific energy consumption, increasing

drilling speed causes an increase in specific energy, especially with used bit. As

shown in figures (4-16, 4-18) for Zaraby limestone and white marble, as examples

when using new at 90 kg WOB and 1000 rpm, the required specific energy is 1.25,1.6

times that at 300 rpm respectively. At the same conditions, using used bit the required

specific energy is 1.34, 1.74 times that at 300 rpm respectively. At 210 kg WOB and

1000 rpm for black granite figure (4-20), the value of energy consumption is 1.67-1.9

times that at 300 rpm.


in black granite, Aswan

Tables 4.4 & 4.5 introduce the correlation equations of the relationships

between Specific energy (SE, Mpa) and weight on bit (WOB, Kg) for all tested rocks

at 300 rpm and 1000 rpm respectively.

0

50000

100000

150000

200000

250000

300000

0 100 200 300 400 500 600

Spec

ific

ener

gy (

SE

), M

pa






66


rocks at 300 rpm

Rock

type

New bit

*R

Used bit *R

Mankabad

limestone

SE= 0.2404 WOB2 -17.063 WOB+358.36 0.92 SE= 0.195WOB

2 -13.762 WOB+373.72 0.92

Minia

limestone

SE= 0.0389 WOB2 -5.657 WOB +296.76 0.93 SE= 0.03 WOB

2 – 4.2285 WOB +335.7 0.69

Assiut

limestone

SE= 0.1273 WOB2 -14.401WOB +512.66 0.85 SE= 0.092 WOB

2 - 10.644 WOB +550.9 0.73

Issawyia

limestone

SE= 0.0752 WOB2 -9.2216WOB +463.51 0.86 SE= 0.0913 WOB

2 -10.841 WOB +573.82 0.74

Zaraby

limestone

SE= 0.1054 WOB2 -13.98 WOB +741.5 0.80 SE= 0.1534WOB

2 -17.244 WOB +687.66 0.79

white

marble

SE= 0.4514 WOB2 -61.07 WOB +2309 0.86 SE= 0.0999 WOB

2 – 3.1057 WOB

+219.29

0.88

black

marble

SE= 0.2853 WOB2 -38.156WOB +1749.5 0.90 SE= 0.3713 WOB

2 – 50.469 WOB

+2255.9

0.92

pink

granite

SE= 0.3094 WOB2 -119.36WOB+14190.06 0.98 SE= 0.6357WOB

2 – 200.12 WOB +20100 0.78

black

granite

SE= 0.0836 WOB2 -61.938WOB +14374 0.97 SE= 0.0744 WOB

2 -54.597 WOB +16103 0.88


rocks at 1000 rpm

Rock type New bit

*R

Used bit *R

Mankabad

limestone

SE= 0.2697 WOB2 -19.458 WOB +484.28 0.91 SE= 0.2034WOB

2 -14.816 WOB +565.34 0.91

Minia

limestone

SE= 0.0424 WOB2 – 5.7987 WOB +406.8 0.92 SE= 0.1115WOB

2 – 15.651 WOB

+840.91

0.93

Assiut

limestone

SE= 0.111 WOB2 – 13.877 WOB +801.82 0.82 SE= 0.2166 WOB

2 – 27.897 WOB

+1272.1

0.92

Issawyia

limestone

SE= 0.2101 WOB2 – 25.586 WOB +1043.5 0.88 SE= 0.2385 WOB

2 – 30.394 WOB

+1365.4

0.89

Zaraby

limestone

SE= 0.05224 WOB2 – 1.40 WOB +127.69 0.75 SE= 0.287 WOB

2 – 41.5 WOB +1859.1 0.91

White

Marble

SE= 0.6453 WOB2 -61.78 WOB + 1198.74 0.93 SE= 0.8499WOB

2 -123.09 WOB + 5256.8 0.91

Black

marble

SE= 0.3469WOB2 – 45.568 WOB +2218 0.78 SE= 0.7345WOB

2 – 105.73WOB +4955.1 0.85

Pink

Granite

SE= 0.6453 WOB2 – 207.17 WOB +21183 0.79 SE= 1.6414WOB

2 – 620.14 WOB - 65673 0.96

Black

granite

SE= 0.9413 WOB2 – 320.83WOB +35710 0.79 SE= 1.7685 WOB

2 – 683.18WOB +76589 0.94


67

The best drilling conditions for all tested rocks are given in Table 4.6. Also,

some of the predicted values of both rate of penetration (ROP) and Specific energy

(SE) are introduced in Tables 4.7 & 4.8 for some tested rocks.

Table ‎4.6: Best drilling conditions for all tested rocks

Rock

type

V1=300 RPM V2 =1000 RPM


WOB,

Kg

ROP,

cm/min.

SE,

MPa

WOB,

Kg

ROP,

cm/min.

SE,

MPa

WOB,

Kg

ROP,

cm/min.

SE,

MPa

WOB,

Kg

ROP,

cm/min.

SE,

MPa

Mankabad

limestone 60 9.83 103.70 60 5.85 170.5 60 19.53 174 60 10.18 326

Minia

limestone 105 12.16 94.54 105 7.3

154.3

105 13.67 280.33 105 8.65 433.9

Assiut

limestone 90 9.53 118.10 90 5.21

211.6

90 11.25

333.6

90 9.3 362.3

Issawyia

limestone 90 6.6 167 90 4.87

221.5

90 13.32

275.8

90 9.68 371.4

Zaraby

limestone 90 4.22 348.2 90 3.67 392.4 90 11.26 435 90 9.13 525.7

white

marble 90 4 509.63 90 2.76 725.71 90 7.66 887.08 90 5.78 1155.1

black

marble 90 4.11 47869 90 3.56 542.7 90 10.33 634.9 90 6.86 937.3

pink

granite

210 2.09 2914.7 210 1.002 4802.31 210 3.14 5227.63 210 2.48

5467.51

black

granite

480 4.8 3004.8 480 2.63 5363 240 2.89 8311 240 2.4 9794

Table ‎4.7: Predicted values of drilling rate (ROP, cm/min.) at the best weight on bit (WOB) as

an example for tested rocks

Rock

Type

Best

Weight

on bit

(WOB),

Kg

V1=300 RPM V2 =1000 RPM


Meas*.

Calc*.

%

Diff.

Meas*.

Calc*.

%

Diff.

Meas*.

Calc*.

%

Diff.

Mea*s.

Calc*.

%

Diff.

Zaraby

limestone

90 4.22 3.84 9 3.67 3.44 6.27 11.26 10.13 10.04 9.13 8.38 8.21

White

marble

90 4.00 3.77 5.75 2.76 2.44 11.59 7.66 6.87 10.31 5.78 5.45 5.71

Pink

granite

210

2.09 2.22 -6.2

1.002 0.95 5.19 3.14 3.00 4.46 2.48 2.30 7.26

68

Table ‎4.8: Predicted values of Specific energy (SE, Mpa) at the best weight on bit (WOB) as

an example for tested rocks

Rock

Type

Best

Weight

on bit

(WOB),

Kg

V1=300 RPM V2 =1000 RPM


Meas*

.

Calc*.

%

Dif

f.

Meas*

.

Calc*.

%

Diff

.

Meas*

.

Calc*.

%

Diff.

Meas*.

Calc*.

%

Diff.

Zaraby

limeston

e

90

348.2

337.04

3.1

392.4

378.24

3.6

435

424.85

2.33

525.7

448.5

15

White

marble

90

509.63

469.40

7.89

725.71

749.74

-3.3

887.08

865.47

2.44

1155.1

1062.9

8

Pink

granite

210

2914.7

2769

5.0

5937.8

6109.2

-2.9

6466.8

6135.03

5.13

7996.6

7829.3

2.1

Meas*. : Measured value.

Calc*. : Calculated value.

4.4 Relationships between rate of penetration (ROP) and specific energy (SE) for all

tested rocks

Curve fitting was made to obtain the mathematical relationships between rate of

penetration (ROP) and specific energy (SE) for all types of tested rocks. Correlation

coefficients were given for all tested rocks. Figures (4.21 to 4.29) illustrate the

relationships between rate of penetration (ROP) and specific energy (SE) for

Mankabad, Minia, Assiut, Issawyia, and Zaraby limestone respectively, at both speeds

300, 1000 rpm using new and used bits. It can be seen that specific energy (SE) is

inversely proportional with the rate of penetration (ROP) in all tested rocks. But

Mankabad limestone requires the least amount of specific energy compared with other

types of tested limestone, while, Zaraby limestone requires the highest amount of

specific energy compared with other tested types of limestone rocks. The lower value

of specific energy indicates that the bit is drilling more efficiently. For granites, at

WOB of 210 kg and drilling speed of 1000 rpm the specific energy consumed is 1.5,

1.9 times which consumed at 210 kg and 300 rpm. For Limestone and Marbles, at

constant weight on bit of 90 kg and drilling speed of 1000 rpm, the specific energy

consumed is 1.25, 1.34 and 1.59, 1.74 times that consumed at 300 rpm respectively.

69

Figure ‎4.21: Relation between rate of penetration and Specific energy at 300 and 1000

rpm in Mankabad Limestone, Assiut


rpm in Beni-Khalid, Samalout Limestone, Minia

50

100

150

200

250

300

350

400

0 5 10 15 20 25

Sp

ecif

ic e

ner

gy (

SE

), M

pa

Rate Of Penetration (ROP), cm/min.

V1=300 rpm (New bit)

V1= 300 rpm (Used bit)



0

100

200

300

400

500

600

700

0 5 10 15 20

Sp

ecif

ic e

ner

gy (

SE

), M

pa

Rate of penetration (ROP), cm/min.





70


rpm in Assiut cement company quarry Limestone, Assiut


rpm in Issawyia Limestone, East Sohag

100

200

300

400

500

600

700

800

900

1000

0 2 4 6 8 10 12 14

Sp

ecif

ic e

ner

gy (

SE

), M

pa






0

100

200

300

400

500

600

700

800

900

1000

0 2 4 6 8 10 12

Sp

ecif

ic e

ner

gy (

SE

), M

pa






71


rpm in Zaraby Limestone, Assiut


rpm in Black Marble, Wadi-El-Miah, Eastern Desert

200

400

600

800

1000

1200

1400

0 2 4 6 8 10 12

Sp

ecif

ic e

ner

gy (

SE

), M

pa






200

600

1000

1400

1800

2200

0 2 4 6 8 10 12

Spec

ific

en

ergy (

SE

), M

pa






72


rpm in White Marble, Wadi-El-Miah, Eastern Desert


rpm in Pink Granite, Aswan

0

500

1000

1500

2000

2500

3000

0 2 4 6 8 10

Sp

ecif

ic e

ner

gy (

SE

), M

pa






0

2000

4000

6000

8000

10000

12000

14000

16000

0 0.5 1 1.5 2 2.5 3 3.5

Spec

ific

ener

gy (

SE

), M

pa






73


rpm in Black Granite, Aswan

Table ‎4.9: Correlation equations of the relationship between (SE) and (ROP) for tested rocks

at 300 rpm

Rock

type

New bit

*R

Used bit *R

Mankabad

limestone

SE= 0.1192 ROP2 -4.0862 ROP +132.31 0.99 SE= 0.0652ROP

2 -3.5775 ROP

+189.57

0.98

Minia

limestone

SE= 1.5107 ROP2 – 28.49 ROP +224.49 0.97 SE= 0.8556ROP

2 – 22.035

ROP+270.78

0.99

Assiut

limestone

SE= 3.0766 ROP2 – 48.079 ROP +305.43 0.96 SE= 3.4729 ROP

2 – 53.409 ROP

+394.45

0.99

Issawyia

limestone

SE= 4.752 ROP2 – 57.386 ROP +345.35 0.98 SE= 5.2049 ROP

2 – 66.433 ROP

+418.97

0.99

Zaraby

limestone

SE= 10.882 ROP2 – 100.24 ROP +577.67 0.99 SE= 14.39 ROP

2 – 120.8 ROP +

643.9

0.99

white

marble

SE= 51.972 ROP2 -391.03 ROP + 1245.9 0.99 SE= 89.966ROP

2 -486.99 ROP +

1395

0.99

black

marble

SE= 39.263ROP2 – 289.85 ROP +1016.3 0.99 SE= 74.874 ROP

2 – 467.67 ROP +

1273.6

0.99

pink

granite

SE= 1104 ROP2 – 4367.8 ROP + 6719.7 0.99 SE= 753.88 ROP

2 – 4000.9 ROP –

8017.9

0.99

black

granite

SE= 432.52 ROP2 – 3306.7 ROP + 9138.4 0.97 SE= 863.33 ROP

2 – 4564.7 ROP +

11495

0.99

0

5000

10000

15000

20000

25000

30000

0 1 2 3 4 5 6

Sp

ecif

ic e

ner

gy (

SE

), M

pa

Rate of prnetration (ROP), cm/min.





74

Table ‎4.10: Correlation equations of the relationship between (SE) and (ROP) for tested

rocks at 1000 rpm

Rock

type

New bit

*R

Used bit *R

Mankabad

limestone

SE= -0.0294 ROP2 – 1.954 ROP +

223.87

0.99 SE= -0.2178 ROP2 – 3.5567 ROP +

370.64

0.99

Minia

limestone

SE= 0.7637 ROP2 – 21.606 ROP +355.32 0.96 SE= 0.6.3371ROP

2 –

106.95ROP+732.62

0.90

Assiut

limestone

SE= 2.1194 ROP2 – 49.368 ROP +624.91 0.99 SE= 8.7614 ROP

2 – 142.18 ROP

+931.89

0.95

Issawyia

limestone

SE= 3.9167 ROP2 – 83.801 ROP +711.86 0.99 SE= 9.7388 ROP

2 – 153.77 ROP

+974.56

0.95

Zaraby

limestone

SE= 2.5934 ROP2 – 70.953 ROP +914.07 0.97 SE= 14.527 ROP

2 – 222.28 ROP

+1373.7

0.97

white

marble

SE= 20.997 ROP2 -297.4 ROP + 1942.1 0.99 SE= 79.827 ROP

2 -821.77 ROP +

3268.4

0.99

black

marble

SE= 2.759ROP2 – 85.812 ROP +1228.5 0.99 SE= 42.746 ROP

2 – 552.22 ROP

+2729.5

0.99

pink

granite

SE= 183.14 ROP2 – 1851.7 ROP + 9263 0.99 SE= 2618.2 ROP

2 – 11917 ROP -

19958

0.99

black

granite

SE= 655.48 ROP2 – 4415.5 ROP + 15608

0.99

SE= 6194.9 ROP2 – 24716 ROP +

34295

0.97


It is clear that the three categories of rocks, Zaraby limestone, White marble

and Black granite are the hardest formations in all tested rocks. As an example, to

obtain the rate of penetration of 2 cm/min. at 300 and 1000 rpm using new and used

bit, Black granite requires an amount of specific energy 9.52, 13.64 and 6.15, 7.5 times

that for Zaraby limestone and White marble respectively.

4.5 Identifying the rock type to be drilled using drilling parameters

In this section a study to calculate the specific energy consumed during the

drilling tests for all tested rocks, and comparing these energies for each rock type is

carried out. Thereafter, a new index (UCS/SE) as a ratio between uniaxial compressive

strength of rock and specific energy of drilling machine is calculated for all tested

rocks at different loads and different rotary speeds. Relationships between UCS/SE

and rate of penetration (ROP) which are previously calculated by using different

weights on bit and rotational speeds, for sedimentary (limestone), metamorphic

(marbles), and igneous (granites) were plotted.

75

Specific energy (SE) is calculated for all types of rocks by using the following

equation [69, 70, 71]:

(‎4.3)

Where:

W= Weight on bit, (kg)

N=Revolution per min.

D= Diameter of bit (mm), and

= Penetration rate ( ⁄ ).

SEV = Specific energy,

⁄

Note that, the quantity SEV has the same dimensions as the stress and that a

convenient unit for specific energy is the Mpa (an equivalent unit for specific energy is

the ( ⁄ ) which is numerically identical to MPa) [5].

The study will concentrate on the calculation of the specific energies consumed

during drilling tests for all tested rocks and comparing these energies for each rock

type. Thereafter, a new index UCS/SE is calculated for all tested rocks at different

loads and rotary speeds. Relationships between the rate of penetration and specific

energy for all rocks are determined to give a comparison between the consumption of

energy in three types of rock being drilled. Relationships between UCS/SE and the rate

of penetration (ROP) are also derived for sedimentary (limestone), metamorphic

(marbles) and igneous rocks (granites).

4.5.1 I -Variation of specific energy with the rock types

Values of drilling rate and specific energy for limestone, marbles and granites

have been averaged and one value for each applied rotary speed represents each rock

group. Each average value of drilling rate and specific energy was determined as an

arithmetic mean for the values of each rock group related to nominal speed. Tables (3-

76

14) and (3-15) of chapter (3) above give the average values of the specific energy and

UCS/SE for limestone, marbles and granites at 1000 and 300 rpm and different loads

for the new bit respectively.

Curve fitting was made for the average values of drilling rate to obtain

empirical equations representing the relationship between specific energy (SE) and

Rate of penetration (ROP) of different rocks[72, 73, 74]. Both experimental and

fitting values of the rate of penetration (ROP) were plotted against the specific energy

(SE) for all rocks at the applied different loads on bit (WOB) as shown in figures (4-

30) and (4-31). The most suitable mathematical equations to fit the data were given

and written, related to each curve in the figures. Figures (4-30, 4-31) show that the

specific energy for all tested rocks at 1000 and 300 rpm and under different loads for

the new bit decreases with the increase of drilling rate. As the thrust load increases,

the work lost in friction will constitute a rapid decrease in the total work done. This

effect will contribute to a fall in specific energy. However, this fall will not continue

indefinitely, a stage may be reached when the tool is pushed so heavily into the rock

that it becomes overloaded and clogs.

The figures generally show the specific energy for all rocks decreased with

increased drilling rate. Comparing the plotted data on Figures 4.28 & 4.29, it can be

seen that as the drilling rate was increased, the magnitude of the change in specific

energy was not the same for limestone, marble and granite. Then, the igneous rock

types had lower drilling rates and higher specific energy than the metamorphic and

sedimentary rock types under investigation.

From Tables 3.14 & 3.15 for different rocks at 1000 and 300 rpm and at

different loads, the marbles needed an amount of specific energy from 2.7, 3.55 times

that of limestone. The granite rocks needed specific energy from 13.19, 14.80 times

that of marbles, and from 36.17, 51.26 times that of limestone needed to complete this

operation at 90kg WOB.

77

Figure ‎4.30: Relationship between average rate of penetration and specific energy for

all rocks at different loads and drilling speed of 1000 rpm

Figure ‎4.31: Relationship between average rate of penetration and specific energy for

all rocks at different loads and drilling speed of 300 rpm

0

2000

4000

6000

8000

10000

12000

0 20 40 60 80 100 120 140

Rate of penetration (ROP, mm/min.)

Sp

ecif

ic e

nerg

y (

SE

, M

Pa)

Limestone

Fitting

Marble

Fitting

Granite

Fitting

SE=-1.8324 ROP + 532.68

SE=0.1003 ROP^2 - 18.242 ROP +1596.5

SE=21709 ROP ^ -0.3088

SE = -2.1508 ROP + 301.72

SE = 10153 (ROP)-0.3218

0

1000

2000

3000

4000

5000

6000

7000

0 20 40 60 80 100

Rate of penetration (ROP, mm/min.)

Sp

ec

ific

en

erg

y (

SE

, M

Pa

)

Limestone

Fitting

Marble

Fitting

Granite

Fitting

SE = -12.398 ROP + 42.91

78

4.5.2 II- Relation between UCS/SE and ROP

On the other hand, specific energy and the dimensionless index UCS/SE were

determined for the three types of rocks at the applied rotary speeds 300 and 1000 rpm

and at different loads as given before in Tables 3.11 to 3.13. The results of

calculations at applied rotary speeds 300 and 1000 rpm and at different loads for new

bit are obtained. The rate of penetration is plotted against the dimensionless index

UCS/SE for all rocks as shown in Figures 4.32 & 4.33. About 48 points are plotted

together representing the sedimentary, metamorphic and igneous rocks from which, 28

points represent 5 limestone at six different loads and two different rotary speeds, 10

points represent marbles (2 types) at five different loads and two different rotary

speeds, and 10 points represent granites(2 types, one of them at eight different loads

and 300 rpm and the other at five different loads and 1000 rpm). It can be seen that

there is no distinct areas for the three types of rocks.

Figure ‎4.32: Relationship between UCS/SE and Rate of penetration for all rocks at

different loads and rotary speed of 1000 rpm, new bit

0

20

40

60

80

100

120

0 20 40 60 80 100 120

Rat

e o

f pen

etra

tion (

RO

P),

mm

/min

.

Index ((UCS/SE)*10^-3

Limestone

Marble

Granite

79

Figure ‎4.33: Relationship between UCS/SE and Rate of penetration for all rocks at

different loads and rotary speed of 300 rpm, new bit

Increasing the rotary speed from 300 to 1000 rpm will increase the penetration

rate by high values in case of limestones but it is not the same in case of marbles and

granites as mentioned before. Then , excluding again the values of rate of penetration

(ROP) against the dimensionless index (UCS/SE) at the same loads but at rotary

speed 300 rpm to see if the three rocks are to fall into distinct zones. Figure (4-34)

represents the results at loads 45, 60, 75, 90, 120, 150, 180, 210, 300, 390 and 480 kg

and at rotary speeds 300 rpm for the new bit.

In Figure 4.34, it is clear that there are only two distinct zones one for

limestones alone and the other for both marbles and granites. It can be concluded that

at higher rotary speed and lower loads for drilling the three types of rocks

(representing sedimentary, metamorphic and igneous) are lying in three distinct zones.

At higher loads and lower rotary speed there are only two distinct zones one for

seimentary and the other for metamorphic and igneous together. Increasing the

0

50

100

150

200

0 10 20 30 40 50 60 70

Rat

e o

f p

enet

rati

on (

RO

P),

mm

/min

.

Index (UCS/SE)*10^-3

Limestone

Marble

Granite

80

mechanical energy level on a bit (or increasing thrust load and rotary speed) will

increase the penetration rate if there is a sufficient hydraulic energy available for

bottom hole cleaning. Increasing thrust load and rotary speed, however, accelerate bit

cutting and wear. In soft formations a doubling of either load or rotary speed will

double penetration rate if sufficient horsepower is available. In hard formations the

load has to be sufficient to overcome the compressive strength of the rock, then

increasing the load on bit by a factor of two doubles or more doubles the penetration

rate.

The penetration rate is not linearly proportional to rotary speed in drilling hard

formations because some finite time is required for a bit to fracture the rock .

Accordingly, as can be seen from Figure 4.32 & 4.33 increasing loads on bit increases

penetration rate by high values in limestones and does not increase it for marbles and

granites by the same values. Also Figures 4.32 & 4.33 show that, at both rotary

speeds 1000 and 300 rpm for all applied loads respectively, the values of the rate of

penetration (ROP) were plotted against dimensionless index (UCS/SE) for all rocks.

The values related to rock types are close to each other. Accordingly, there is no

distinct areas for each rock type. If we exclude the rates of penetration that

correspond to the lower loads 15 and 30 kg using lower speed (300 rpm), it would be

seen that the three groups of rocks are lying only into two distinct areas, one for

sedimentary and the other for both metamorphic and igneous rocks together as shown

in Fig. 4.34.

81

Figure ‎4.34: Relationship between UCS/SE and rate of penetration for all rocks at

rotary drilling of 300 rpm and loads of 45, 60, 75, 90, 120, 150, 180, 210,

300, 390 and 480 kg, new bit

Figure ‎4.35: Relationship between UCS/SE and rate of penetration for all rocks at

rotary drilling of 1000 rpm and loads of 45, 60, 75, 90, 120, 150, 180,

210, 300, 390 and 480 kg, new bit

0

20

40

60

80

100

120

0 20 40 60 80 100 120

Ra

te o

f p

en

etr

ati

on

(R

OP

),

mm

/min

.

Limestone

Marble

Granite

Index UCS/SE X 10^-3

Limestone

Marble + Granite

0

50

100

150

200

250

0 10 20 30 40 50 60 70

Rate

of

pe

netr

ati

on

(R

OP

), m

m /

min

.

Limestone

Marble

Granite

Index UCS/ES X 10^-3

82

CHAPTER 5

5 CONCLUSIONS AND RECOMMENDATIONS

Drilling trials are conducted on three types of rocks, sedimentary rocks namely,

Mankabad, Assiut cement company quarry, and Zaraby limestone, Assiut. Issawyia

limestone, East Sohag and Beni-Khalid, Samalout limestones, Minia. Metamorphic

rocks namely, white and black marbles, from Wadi El-Miah, Eastern Desert, and

igneous rocks namely, pink and black granites from Aswan. By using a stationary

laboratory- drilling machine over a range of weights on bit. (WOB = 15, 30, 45, 60,

75, 90, 105 and 105 kg) for sedimentary tested rocks (limestones) and (WOB = 30, 45,

60, 75 and 90 kg) for metamorphic tested rocks (marbles), and the loads on bit for

granites (WOB= 90, 120, 150, 180, 210, 240, 300, 390, 480 and 570 kg). All tests

were carried out at 300 and 1000 rpm using new and used bit.

Physical properties (density and porosity) and mechanical properties (compressive

strength, tensile strength, shear strength, and coefficient of internal friction) were

measured to give a complete description about the tested rocks as given in Table 3.1.

Relationships between both weight on bit, rate of penetration, specific energy, and

torque. Rate of penetration and specific energy were given, Figs. 4.1 to 4.29.

Relationships between WOB and both ROP and SE were determined. The results for

ROP are high correlated with the operating parameters. Rate of penetration increases

rapidly in Zaraby limestone (hardest type of all tested limestone) with increasing

weight on bit. Maximum value of penetration rate and minimum value of energy

consumption was obtained at weight on bit of 90 kg WOB, so this value is considered

the best weight on bit. The highest value of the rate of penetration ROP was obtained

during drilling limestones by using small weight on bit and high drilling speeds, while

it can be obtained by using heavy weights on bit and small drilling speeds in Marbles

and Granites. So that, it is recommended to use small WOB and high speeds with

weak rocks and vice versa with hard rocks.

83

The effect of bit condition upon the drilling parameters, for example, in Zaraby

limestone when using a new bit for drilling the rate of penetration (ROP) is 1.15 – 1.23

times that of used one. For white marble, the rate of penetration when using a new bit

is 1.45 – 1.33 times that of used bit. Also for pink granite introduces that the rate of

penetration (ROP) with new bit is 2-1.27 times that of used one. From the economic

point of view, the rate of penetration (ROP) in the weak rocks is less influenced when

using new and used bits than with hardest rocks, so that, it is recommended to use bits

for longer periods of time to drill weak rocks, in comparison with hard rocks, where

the time periods are to be shorter. For the three types of rocks, the best drilling

conditions were summarized in Table 4.21. The results have revealed that, the best

weight on bit (WOB) is that gives maximum rate of penetration (ROP) and minimum

amount of specific energy consumption (SE).

The specific energy for drilling in different categories of rocks were obtained by

using diamond core drilling. It is noticed that the specific energy (SE) decreases by

increasing weight on bit (WOB) until a certain limit and then it is either constant or

begins to increase. The lower values of specific energy (SE) indicate that the bit is

drilling more efficiently in limestones than the other two rocks. To achieve low values

of specific energy (SE), it is obviously advantageous to have rate of penetration as a

high as possible. The variation in specific energy for all rocks at applying different

loads and different rotary speeds were discussed. It is found that the marbles needed

amount of specific energy from 2.7-3.55 times that of limestones. The granite rocks

needed specific energy from 13.19-14.8 times that of marbles, and from 36.17-51.26

times that of limestones needed, according to applied loads, to complete this operation.

Relationships between rate of penetration (ROP) and specific energy (SE) for all

types of rocks at different loads and different rotary speeds were obtained and plotted

in Figures 4.30 & 4.31. The dimensionless index (UCS/SE) is calculated and given in

Tables 3.11 to 3.13. The relationships between the rate of penetration (ROP) and

(UCS/SE) were plotted at different thrust loads and different rotary speeds as shown in

Figures 4.32 to 4.35. Determining the new index (UCS/SE), we can specify the rock

84

type and its penetration rate. The following Table 5.1 gives the range of drilling

parameters values related to the three types of rocks.

Table ‎5.1: The range of drilling parameters values related to the three types of rocks

Type

Of

Rock

WOB,

Kg

T,

N.m

ROP,

Cm/min

SE,

MPa

(UCS/SE)*10-3

300

RPM

1000

RPM

300

RPM

1000

RPM

300

RPM

1000

RPM

Limestone

From

To

15

90

2.1

12.4

0.47

4.22

0.93

11.26

529.5

348.2

892

435

49

77.69

24.84

62.18

Marbles

From

To

]30

90

5.5

17.21

0.79

4

2.02

7.66

825.13

509.63

1077.4

887.08

49.14

100.7

37.6

57.9

Granites

From

To

90

480

22

119

0.4

4.8

0.9

-

6518.3

3004.8

9656.8

-

11.5

31.7

7.75

-

The results indicated that at all applied loads and two drilling rotary speeds (300

and 1000 rpm) there is no distinct zones. Whereas, at higher applied loads and lower

rotary speeds (300 rpm) the three groups of rocks are lying into two zones only: one

for sedimentary and the other for metamorphic and igneous. But, at higher applied

loads and higher rotary speeds (1000 rpm) the three groups of rocks are lying in three

distinct zones. In addition to other information obtained from the analysis of drill

cuttings, it can be possible to identify the actual rock type to be drilled. Future

researches related to drilling parameters as a tool of rock characterization which is

subject of this thesis may be recommended, namely: to discuss the use of different

rotary speeds other than 300 and 1000 rpm with different loads, and also to discuss the

drilling behavior related to other types of rocks.

85

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