Summary
Generally, in classical reservoir studies, the geomechanical behavior of the
porous medium is taken into account by the rock compressibility. Inside the
reservoir simulator, the rock compressibility is assumed to be constant or to
vary with the pressure of the oil phase. It induces some changes in the
porosity field.
During the depletion phase or the cold-water injection of
high-pressure/high-temperature (HP/HT) reservoirs, the stress state in and
around a reservoir can change dramatically. This process might result in rock
movements such as compaction, induced fracturing, and enhancement of natural
fractures and/or fault activation, which continuously modify the reservoir
properties such as the permeabilities and the fault transmissibilities.
Modifications of such parameters strongly affect the flow pattern in the
reservoir and ultimately the recovery factor.
To capture the link between flow and in-situ stresses, it becomes essential
to conduct coupled reservoir-geomechanical simulations.
This paper compares the use of five types of approach for the reservoir
simulations:
-
A classical approach with rock compressibility using only a reservoir
simulator.
-
A loose coupled approach between a reservoir simulator (finite volumes) and
a geomechanical simulator (finite elements). At given user-defined steps, the
hydrocarbon pressures calculated by the reservoir simulator are transmitted to
the geomechanical tool, which computes the actual stresses and feeds back
iteratively the modifications of the petrophysical properties (porosities and
permeabilities) to the reservoir simulator.
-
A one-way coupling: this approach is a simplification of the loose coupled
approach in that the modifications are not fed back to the reservoir
simulator.
-
A simplified approach using permeability and porosity multipliers inside a
reservoir simulator. These multipliers are user-defined curves and vary with
the pressure of the oil phase. This approach uses only a reservoir
simulator.
-
A coupled approach in which the structural and the flow unknowns
(displacement, pressure, and saturations) are solved simultaneously.
These approaches are compared for two validation cases and two field cases
described in the following.
© 2006. Society of Petroleum Engineers
View full textPDF
(
3,723 KB
)
History
- Original manuscript received:
3 February 2003
- Revised manuscript received:
28 July 2005
- Manuscript approved:
30 October 2005
- Version of record:
20 March 2006
View Cart
