pipeline design & integrity seminar - presentation 1

www.crondall-energy.com All rights reserved

Higher Quality Inspection of Deepwater Flowlines will Save Costs On Future Projects Crondall Energy Subsea 17 June 2015


WHO are we?

Independent Engineering Consultancy Floating Production & Subsea Specialists Focus:

Ø  Facilities Engineering Ø Marine Technology Ø  Subsea Engineering

•  Challenging HPHT & Deepwater •  Concept Development •  Flow Assurance •  Subsea Hardware •  Design Verification •  Research & Development •  Failure Investigations

Aberdeen

Winchester

Newcastle

Amsterdam

Singapore

Perth

Houston

© Crondall Energy Subsea Ltd 2015 2


Higher Quality Inspection of Deepwater Flowlines will Save Costs On Future Projects

Ø Why is Survey Quality important? Ø What do we mean by Good Quality? Ø Integrity Monitoring Lessons Ø Design Lessons for Future Projects Ø Potential Cost Savings?

3 © Crondall Energy Subsea Ltd 2015


Why is survey quality important?

Pipelines can move: Ø  Lateral motion

•  Lateral buckling •  Route curve pullout

Ø  Axial motion • Pipeline walking • Expansion at ends and

into lateral buckles


Ø  Lateral buckling •  Railway tracks •  Pipelines

Ø  Walking: •  Stones in Death valley •  Global pipeline movement

Measurement of pipe-walking


Pipelines have failed due to lateral buckling, Ø  3 involved full bore rupture Ø  1 involved premature abandonment

5

Lateral Buckling

Side-scan sonar image of lateral buckle

ROV Camera

Bruton & Carr OTC 21671 (2011) © Crondall Energy Subsea Ltd 2015


Engineered Buckle Initiators

6

Snake Lay

Sleepers (vertical upset)

Buoyancy (local weight reduction)

Bruton & Carr OTC 21671 (2011) © Crondall Energy Subsea Ltd 2015

www.crondall-energy.com All rights reserved 7

Pipeline Walking

Pipe-walking occurs during shutdown/restart cycling, when: Ø  Tension is applied by riser, Ø  Seabed slope along route Ø  Liquids and gas segregate at shutdown Ø  Steep thermal transients in operation

Pipe walking has caused several pipeline failures Ø  Tie-in spool failures due to overload, other spools close to failure Ø  Several lines have been rock dumped or anchored to prevent further walking

© Crondall Energy Subsea Ltd 2015

Bruton & Carr OTC 21671 (2011)


Walking may be controlled by the use of pipeline anchors Several deepwater projects have installed pipeline anchors Ø  Typically suction piles with a capacity of 50 to 350 tons

Key drivers in the layout of a field development. But high levels of tension at shutdown can be a concern: Ø  Route-curve becoming unstable and pulling out – one observed Ø  Buckles pulling-straight & not reforming – observed in the field

8

Pipeline walking control

AnchorFlowline

Floating Production System

SCRAnchorFlowline

Floating Production System

SCR


Jayson et al OPT 2008


Pipe-soil Interaction

Pipe soil response is the most significant uncertainty in design for lateral buckling, pipeline walking, route-curve pullout and flowline anchoring

Significant research effort to evaluate, quantify and understand the complex pipe-soil interaction mechanisms.



0.00

0.20

0.40

0.60

0.80

1.00

1.20

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4Lateral Friction Coefficient

Usa

ge F

acto

r

Girth Weld Fatigue LimitLocal buckling LimitStrain Capacity Limit

Design limit

2.5km VAS

2.0km VAS

10

Why is pipe-soil resistance important

Axial pipe-soil resistance affects: Ø  Maximum axial force in the pipeline

•  Influencing buckle formation •  Compression at crossings & in-line

structures •  Shutdown tension

Ø  Pipe displacement •  Pipe-end expansion •  Feed-in to lateral buckles •  Pipeline walking rate

Lateral pipe-soil resistance affects: Ø  Lateral restraint for buckle formation Ø  Route-curve stability under axial tension Ø  Lateral buckle bending loads Ø  Cyclic buckle loading due to soil berms. Aim to bound the pipe-soil resistance & ensure that design is acceptable throughout potential design envelope.

1.5km a = 0.1

3km a = 0.1

4km a = 0.1

1.5km a = 0.58

3 km a = 0.580

100

200

300

400

500

600

0 0.5 1 1.5 2Seabed Slope (degrees)

Wal

k (m

m/

cycl

e)


Bruton et al OSIG (2007)


Large scale pipe-soil interaction tests

11

Axial test set up

Lateral test set up

NGI Oslo

Large-scale tests explored axial & lateral pipe-soil resistance in various soils



Fugro SMARTPIPE® in-situ testing

Deepwater PSI testing in-situ on seabed in West Africa and Australia



Small-scale lateral pipe-soil tests in centrifuge

University of Western Australia

Small-scale lateral pipe-soil tests in a centrifuge, Employed on many current projects



Laboratory versus Field data

Ø Laboratory learnings from PSI testing has been invaluable

Ø Field data from observation of real behaviour is incredibly valuable but often not realised



Inspection Surveys & Site Investigations

Integrity monitoring is essential for laterally buckling & pipeline walking 1.  Vital to safe long-term performance and system integrity 2.  Of significant benefit to future projects

Ø  Advances understanding Ø  Calibrate models used in design

Good Quality Data Required- along the whole pipeline: 1.  Soils Data 2.  Bathymetric data 3.  Embedment data & cross profiles 4.  OOS (Out-of-Straightness) 5.  Digital Terrain Mapping 6.  End Expansions 7.  Operating Conditions (past & at time of survey)


soil berm

mudline

estimate / measure extent of lateral displacement

soil disturbance

Jayson et al OPT 2008 EXAMPLES…..


Soils shear strength data - typical

Shear strength data bounded with little recognition of near surface variability


Region of interest


Soil shear-strength profiles – good quality

17

Weak slough at the mudline, very low shear strength < 0.5kPa Not to be ignored

Remoulded shear strength measured T-bar (10 cycles) Defines pipe embedment

Stronger crust below mudline, common to many deepwater sites Provides lateral resistance



Embedment Data

Near and Far embedment data Usually provided in 5-point file



Embedment survey data – Good Quality

Slide 19

Good quality data

Poor quality data Far embedment error

Bruton OTC 25339 (2014) © Crondall Energy Subsea Ltd 2015

Supplied to Crondall Energy


OOS (out-of-straightness) data

Survey Data Review: Ø  Post lay (as-laid) and Post Hydrotest (as-built) data compared Ø  Large number of lateral OOS features identified post-hydrotest Ø  Question: Do these features indicate on-bottom buckling during hydrotest?


Potential buckle

As-built 3D swathe data: No evidence of sediment disturbance – no buckling!


Use of the Gyro Heading Data

Poor quality As-built (operational) survey Ø  Gyro data used to calculate revised Eastings and Northings for OOS Ø  “Gyro” dataset compares well to as-laid data; removing large lateral offsets from the

original E-N data Ø  Excellent agreement between gyro data and as-laid data, confirming that operational

data is very poor and that suspected buckles are not there


As-built OOS data quality appears very poor and is unreliable


Data Acquisition by ROV

VEHICLE (Position)

ALTITUDE DEPTH

DVL INS

Physical contact, or MBES

PIPELINE POSITION

SONAR (anti-collision, but also feature identification)

PIPELINE RECOGNITION (Pipe Tracker)

•  Horizontal positioning determined using USBL, INS, DVL, MBES •  Vertical (sub-surface) positioning determined using MBES, Digiquartz Depth Sensor

USBL

VESSEL

DGPS

LINE OF POSITION (full transponder array or

‘sparse’ array)


Abbreviations DGPS - Digital Geographic Positioning System DVL – Doppler Velocity Log USBL – Ultra-Short Baseline INS – Inertial Navigation System MBES – Multi-beam Echo-Sounder


ROV Visual Survey

Useful to observe buckle locations and soil berms Impossible to assess bending curvature and load in buckle



Side-scan survey - Lateral Buckle on Sleeper

Side scan survey introduces parallax errors in amplitude - pipe raised off seabed Very difficult to accurately assess buckle curvature



Greater Plutonio – West Africa Block 18

Project led the way in addressing pipe-soil interaction by: Ø  Collecting high quality shear-strength

data in the field , including remoulded shear strength using cyclic T-bar tests, to a depth of about 2m.

Ø  An extensive range of axial and lateral pipe-soil tests to support design, including tests at large-scale using soil collected from the field.

Ø  Effective monitoring of the pipelines in operation, including high-quality (and repeatable) positional surveys and high-resolution terrain mapping

Sadly - many projects fail to do any of this!

25




Remnant of berm from hydrotest

Migration of mode-shape – Initiation by sleeper




Deepwater surveys overcome the challenge of achieving high positional accuracy in deep water by using fully calibrated INS (inertial navigation) High resolution digital terrain imagery is used to assess soil berm response & displacement history Behaviour surprises: Ø  Buckle shape migration and interaction

between lateral buckling and pipe walking Ø  Planned buckles not forming, rogue

(unplanned) buckles forming Ø  Buckle mode shapes differing from design

and changing with operating cycles Ø  Slugging induced fatigue at sleepers and

tie-ins Ø  Higher rates of pipeline walking due to

liquid hold up

27

Integrity monitoring surveys & feedback

0

1

2

3

4

5

6

7

8

-250 -200 -150 -100 -50 0 50 100 150 200 250

Late

ral D

ispl

acem

ent (

m)

Buckle Length (m)

Survey #1

Survey #2

Survey #37

7.05

7.1

7.15

7.2

-20 -10 0 10 20

Good repeatable survey data

Watson, Bruton & Sinclair OTC 21724 (2011)



High Resolution Digital Terrain Mapping

28

Urthaler et al OMAE 2012

High quality survey of buckles with buoyancy in the Gulf of Mexico. High Resolution Digital Terrain Mapping, showing clear soil berms & pipe curvature





Pipeline Buckling – Prediction & Actual

Compare actual buckles with predicted buckles for a range of axial friction Observed increasing buckles with time! Valuable lesson that axial friction is increasing with time Rate of increase (dependent on operating cycles and duration) needs quantifying



Pipeline Walking – Prediction & Actual


Hill & White ISFOG 2015

Compare actual walk with predicted walk based on end expansion for a range of axial friction Valuable lesson that axial friction is increasing with time Rate of increase needs quantifying


Cost Savings from Lessons Learned

Observed response on operating systems leads to: Ø  Improved system integrity Ø  Narrowing of design envelope

Major potential cost saving potential for current projects: Anchors: Ø  Flowlines with three 100t anchors to control walking – at ~$2m per anchor Ø  Reduction to one anchor per flowline is likely – saving $4m per flowline

Buckle Initiators Ø  Flowlines with three or four buoyancy initiators – at ~$1m per initiator Ø  Reduction to two to three initiators – saving $1m per flowline Ø  Some past projects had initiators installed – experience shows probably not needed

No good measurements of pipeline expansion – just snap-shot in time Ø  Continuous measurement possible but not implemented on projects Ø  Retroactive measurement on walking pipelines not effective – poor quality monitoring Ø  Key lessons not learned fast enough!



Higher Quality Inspection of Deepwater Flowlines will Save Costs On Future Projects

Ø Good Quality Surveys are Important! Ø How do we maintain Good Quality? Ø Significant Integrity Monitoring Lessons Ø Many Design Lessons for Future Projects Ø Significant Potential Cost Savings


www.crondall-energy.com


References

Ø  Bruton, D. A. S. & Carr, M., 2011. Overview of the SAFEBUCK JIP. OTC 21671 ed. Houston: Offshore Technology Conference.

Ø  Bruton, D. A. S., Sinclair, F. & Carr, M., 2010. Lessons Learned From Observing Walking of Pipelines with Lateral Buckles, Including New Driving Mechanisms and Updated Analysis Models. Houston, Offshore Technology Conference.

Ø  Bruton, D. A. S., White, D. J., Hill, A. & Langford, T. L., 2009. Techniques for the assessment of pipe-soil interaction forces for future deepwater developments. Houston, Proc. Offshore Technology Conference.

Ø  Bruton, D.A.S., Carr, M. White, D. (2007). The Influence of Pipe-Soil Interaction on Lateral Buckling and Walking of Pipelines – The SAFEBUCK JIP. Sixth International Offshore Site Investigation and Geotechnics Conference - Society of Underwater Technology. P133.

Ø  Jayson, D. et al., 2008. Greater Plutonio Project – Subsea Flowline Design and Performance. Amsterdam: Offshore Pipeline Technology Conference.

Ø  Watson, R., Sinclair, F., Bruton, D.A.S., 2011. SAFEBUCK: Operational Integrity of Deepwater Flowlines. Offshore Technology Conference. OTC 21724.

Ø  Urthaler, Y., Watson, R., Davis, J. 2012 Lateral buckling of deepwater pipelines in operation. . International Conference on Ocean, Offshore and Arctic Engineering. OMAE-83949


pipeline design & integrity seminar - presentation 1

Documents