Petroleum Hydrogeology of the Llanos Basin

Petroleum Hydrogeology of the Llanos Basin:
The Role of Hydrodynamic Stagnation Zones
1Mark Person, 1David Butler, 2Carl W Gable, 3Tomas Villamil, 4David Wavrek, and 5Daniel Schelling
1NM Tech
2Los Alamos National Laboratory
3Grupo C&C Energía, Bogota
4Petroleum Systems International LLC
5Structural Geology International LLC
Person et al. (2012, AAPG Bulletin)
Rubiales
Petroleum Hydrodynamics
Hubbert, M.K. (1953) Entrapment of Petroleum under Hydrodynamic Conditions, AAPG Bulletin
Tilt of Oil‐Water Contact
Lateral Hydraulic Gradient
M.K. Hubbert
z
 w h

x  w   o x
Impossible d’afficher l’image.
 z 
 
 x 
Hydraulic head (h)
Amplification Factor (~5)
Title of oil water contact (z/x)
z
x
Modified Hele‐Shaw Model
Upper Reservoir Head
Glycerine
Outflow Head
Impossible d’afficher l’image.
h
z
6
x
x
z – elevation of oil‐water contact
h – head
w, g – water, glycerin density
Oil Flushing Experiment using Hele‐Shaw Model
Hydrodynamic Stagnation Zones:
Form when groundwater flow directions are opposite of structural slope
Groundwater Flow Direction
Person et al. (2012, AAPG Bulletin)
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 Basin
Giant Oil Field: 501 million barrels
Discovered by Exxon in 1981
Heavy Oil (API 12o; 980 kg/m3 )
No Structural Closure!
z
h
 50
x
x
Heavy Oil Amplification Factor
Gomez et al. (2009)
Observed Hydraulic Head Map, C7 Reservoir
Anomalous Heads
High Heads from Leakage Across Fold & Thrust Belt
Rubiales
Down Dip
Groundwater Flow
Villegas et al. (1995)
Llanos Basin Structure, Temperature, & Salinity Patterns
Villegas et al. (1995)
Anomalous Heads Simulated Hydraulic Heads
Imposed
Head 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
Hydraulic Head (h)
Oil Head (ho)
Elevation (z)
• Hubbert’s Oil Heads
• Oil Density (830 kg/m3)
• Water Density (1000 kg/m3)
Oil Density
Water Density
Impossible d’afficher l’image.
Elevation
Oil Head
Hydraulic
Head
Regional Flow Patterns
NW
SE
Cross‐Sectional Model Calibration