How To Approximate Effects of Geomechanics in Conventional Reservoir Simulation

TLDR

Geomechanics in conventional reservoir simulators is typically represented by pressure‑dependent porosity and permeability, yet no single method universally outperforms others, though reasonable approximations exist for many scenarios. This paper systematically reviews pressure‑dependent approximation methods for geomechanics. It details porosity coupling based on deformation type, provides accurate approximations for uniform depletion under various deformation assumptions, and introduces new permeability‑coupling methods validated against fully coupled simulations. The study demonstrates that simple approaches can produce large errors in estimating reservoir pressure decline and well productivity or injectivity.

Abstract

Abstract Geomechanics is often represented in conventional reservoir simulators by pressure dependent treatment of porosity and/or permeability. The paper gives a systematic treatment of the subject and shows different methods for pressure-dependent approximations. Although there is no single method that would provide the best approximation under all circumstances, reasonable approximations exist in several situations. For porosity coupling, the primary factor is the type of deformation. Accurate approximations are given for the cases of uniform depletion with different deformation assumptions. For permeability coupling, new methods have been developed and tested against coupled simulations. The results show clearly that large errors can result from simple approaches, in estimating both reservoir pressure decline and well productivity/injectivity.