Numerical – Geomechanical Investigation on the Relative Permeability Changes During CO2 Sequestration in Depleted Carbonate Gas Reservoir

ABSTRACT: In this paper, a fully coupled fluid flow and geomechanics simulation is performed to investigate the impacts of geomechanical parameters on relative permeability that may affect both fluid recovery and CO2 storage in the X field, a carbonate gas field located in the Central Luconia Basin, Sarawak. It is observed that by taking into account the effects of geomechanics into simulation model provides effects of deformation of porous media on multiphase systems. Fully coupled simulation geomechanical model indicates a systematic decrease in the gas relative permeability in response to pressure depletion during production. The history matched model is then designed for CO2 sequestration by injecting CO2 with group controls into the gas zone. During injection period, it is observed that there is an increase in gas relative permeability which provides more CO2 stored capacity. It shows that total CO2 stored when incorporating geomechanics effects on the simulation is higher than the model without incorporating geomechanics effects. These findings prove the crucial impact of effective stress-induced pore deformation on multiphase flow properties of rock, which are missing from the current characterizations of multiphase flow mechanisms in porous media, especially for CO2 sequestration. 1. INTRODUCTION It is necessary to understand rock behavior during reservoir development and other technological operations in order to ensure rock stability or cause rockfall and manage these processes. Geomechanics is important in order to account for rock deformations due to pore pressure changes resulting from production and fluid injection (Gutierrez and Lewis, 1998). In this case, the problem of viscous compressible fluid flow in porous media should be coupled with the system of elasticity equations. The geomechanical model describes elastic rock stresses. Relative permeability is one of the governing parameters that characterize multiphase fluid flow in porous media for oil and gas industrial applications including CO2 sequestration. Fluid production and injection in the subsurface formation will lead to pore deformation in response to the pore pressure/stress coupling effect. In this paper, a fully coupled fluid flow and geomechanics simulation is performed to investigate the impacts of geomechanical parameters on relative permeability that may affect both fluid recovery and CO2 storage in the X field, a carbonate gas field located in the Central Luconia Basin, Sarawak.