A fully coupled flow and geomechanics model for a tight gas reservoir: Implications for compaction, subsidence and faulting

For variations in well productivity and reservoir permeability, subsidence and compactions modeling has been widely used in reservoirs worldwide. This paper introduces a mono-dimensional fully coupled multiphase flow and geomechanics solver that can be applied to modeling the effects of withdrawal on subsidence of homogeneous porous media. This is accomplished by considering multiphase flow in deformable porous media which is a multiphysics problem that considers the flow and rock physics simultaneously. To model this problem, the multiphase flow equations and geomechanical equilibrium equations must be tightly coupled. The model presented in this work solves the governing equations based on a fully implicit finite difference approach for pressure, rock displacement and saturation terms in order to be consistent with the widely used reservoir simulators. The simulator developed in this work is then applied for the case study of a section of a tight gas reservoir during the production phase. The results of the numerical simulation capture the complex physics of the system in terms of variation in pore pressure and rock deformation and porosity and saturation changes by considering both Darcy and non-Darcy effects. These results of the developed simulator are compared with the results generated by a commercial software package to test the validity of the code while using data for a tight gas reservoir drilled in the Persian Gulf. It is envisaged that this approach would help in better understanding the intricacies of the processes associated with such complex problems pertaining to reservoir compaction and associated stress changes.