petroleum hydrogeology of the llanos...
TRANSCRIPT
1Mark Person, 1David Butler, 2Carl W Gable, 3Tomas Villamil, 4David Wavrek, and 5Daniel Schelling
1NM Tech2Los Alamos National Laboratory3Grupo C&C Energía, Bogota4Petroleum Systems International LLC5Structural Geology International LLC
Petroleum Hydrogeology of the Llanos Basin:
The Role of Hydrodynamic Stagnation Zones
Rubiales
Person et al. (2012, AAPG Bulletin)
Petroleum Hydrodynamics
Hubbert, M.K. (1953) Entrapment of Petroleum under Hydrodynamic Conditions, AAPG Bulletin
M.K. Hubbert
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Tilt of Oil‐Water Contact
Amplification Factor (~5)
Lateral Hydraulic Gradient
xh
xz
ow
w
Hydraulic head (h)
Title of oil water contact (z/x)
x
z
xz
Modified Hele‐Shaw Model
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z – elevation of oil‐water contacth – headw, g – water, glycerin density
Glycerine
Upper Reservoir Head
Outflow Head
xh
xz
6
Oil Flushing Experiment using Hele‐Shaw Model
Hydrodynamic Stagnation Zones:Form when groundwater flow directions are opposite of structural slope
Person et al. (2012, AAPG Bulletin)
Groundwater Flow Direction
Goal of Study• Do Hydrodynamic Stagnation Zones Exist Within the Llanos Basin?
• If so, where would one expect to find them?
Llanos Basin, Colombia
Oil Reservoirs, Llanos Basin
Rubiales Oil Field, Llanos BasinGiant Oil Field: 501 million barrelsDiscovered by Exxon in 1981Heavy Oil (API 12o; 980 kg/m3 )No Structural Closure!
Gomez et al. (2009)
xh
xz
50
Heavy Oil Amplification Factor
Villegas et al. (1995)
Down DipGroundwater Flow
Anomalous Heads
High Heads from Leakage Across Fold & Thrust Belt
Rubiales
Observed Hydraulic Head Map, C7 Reservoir
Llanos Basin Structure, Temperature, & Salinity Patterns
Villegas et al. (1995)
Anomalous Heads
Simulated Hydraulic Heads
ImposedHead B.C.From Fold Belt
Observed & Simulated Heads, C7 Reservoir
O
‐ Oil Migration Direction
Hydrodynamic Stagnation Zones
Conclusions• For regions with gentle structural slope ( < 1%) and typical water table
topographic gradients ( ~ 0.5 %), groundwater hydrodynamics can create regions where oil is trapped by hydrodynamics without any need for structural closure
• Hydrodynamic Stagnation zones are most likely to form at the distal edge of a foreland basin where erosion and uplift has created down‐dip groundwater flow
• Dry holes in the Llanos Basin with fresh water shows is a bad sign …these venues may have been hydrodynamically flushed in the past.
• Hydrodynamic models of secondary oil migration that used relatively heavy oil densities (12o API gravity) predicted the existence of a stagnation zone in the vicinity of the Rubiales oil field. This implies that the position of this field is in equilibrium with it’s current (water washed) density.
Entrapment of Oil Under Hydrodynamic Conditions
• Hubbert’s Oil Heads• Oil Density (830 kg/m3)• Water Density (1000 kg/m3)
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Oil Head
HydraulicHead
Elevation
Hydraulic Head (h)
Oil Head (ho)
Elevation (z)
Oil DensityWater Density
Regional Flow Patterns
NW SE
Cross‐Sectional Model Calibration