Analysis of pore collapse and shear-enhanced compaction in hydrocarbon reservoirs using coupled poro-elastoplasticity and permeability

Abstract

The withdrawal of fluid from a reservoir results in a decline of the fluid pressure followed by a consequent change in stress state in porous rocks. Stress change may cause irreversible deformation and compaction. Such compaction is generally the result of pore collapse and shear-enhanced compaction caused by changes at a microscopic level in the porous rocks. Pore collapse and shear-enhanced compaction are considered as potential problems during reservoir production and drilling operations. The purpose of this paper is to analyze the pore collapse and shear-enhanced compaction in hydrocarbon reservoirs using coupled poro-elastoplasticity and permeability. In this coupling, the poro-elastoplasticity analysis includes the linear component based on Biot’s theory and the nonlinear component based on a cap plasticity model. The fluid flow formulation is defined by Darcy’s law, including a nonlinear permeability model. The numerical approximation is implemented using continuous finite element approximations for rock deformation and mixed finite element approximation for pore pressure and flux. Several numerical simulations are performed to indicate the onset of pore collapse and shear-enhanced compaction and evaluate their effects on reservoir performance.