Field-scale fully coupled simulation of fluid flow and geomechanics: Gas storage/recovery process in a depleted sandstone reservoir

This work addresses a field-scale model, in which the equations of multiphase/multicomponent fluid flow and geomechanics were fully coupled, to simulate natural gas successive storage/recovery processes in an Iranian sandstone depleted gas reservoir. First, a 1D mechanical earth model was developed for the reservoir wells and then converted to a geomechanical 3D model of the reservoir, through sequential Gaussian simulation. The fully coupled simulation of the fluid flow and geomechanics - validated by the analytical solution of the Mandel's problem - was then performed for ten years of gas injection/production cycles in a section of the reservoir between two wells. Variations of different parameters including porosity, permeability, subsidence and effective stress were investigated versus time and compared to those of the non-fully coupled model, within the 10-year period in the studied section of the reservoir. Moreover, the results of the fully coupled model were compared to that of the non-fully coupled one in terms of the gas production rate and bottom-hole pressure in a single well. The results showed that the maximum rate of gas production as well as the maximum bottom-hole pressure predicted by the fully coupled model were 9.5 and 15% lower than those of the non-fully coupled model, respectively.