Modeling geomechanical responses induced by CO2 injection in CCS pilot project in Gundih field, Indonesia

Abstract

Injection activity changes reservoir pore pressure and temperature condition and then alters stress condition of reservoir. Increasing pore pressure from injection leads to a decrease in effective stress of reservoir rocks and surrounding rocks. It induces deformation and failure on the reservoir, which in turn, might create surface uplift. This process is modelled by a coupled Thermo - Hydro - Mechanics (THM) modelling. Hence, objective of study is to investigate and to simulate geomechanical responses induced by CO2 injection in Gundih Field, as part of Carbon Capture and Storage (CCS) Pilot Project in Indonesia. A 3D model of a layered formation consists of porous and permeable reservoir layer and non-porous and impermeable cap rock is built. A boundary condition is set as no lateral displacement normal to side boundary and no vertical displacement normal to bottom boundary. An injection scheme of 0.32 Kg/s for one year is applied in the reservoir at 900m depth. At this depth, CO2 is a supercritical condition, in which the phase depends on the hydrostatics pressure and gradient thermal. The pressure distribution obtained in this study showed that the stress perturbation around the cap rock due to CO2 fluid injection is relatively small and no failure at the cap rock layer is expected. Hence, the proposed CO2 fluid injection is safe to be executed. The program developed in this study could be used to assess the design of CO2 injection schemes.