Comparative Assessment of Potential Ground Uplift Induced by Injection of CO2 into Ainoura, and Berea Sandstone Formations

AbstractIn this paper, we undertook numerical simulations to predict the uplift ground surface induced by CO 2 injection into sedimentary rocks formations. Ainoura and Berea sandstone cases were selected to represent low and moderate permeability cases, respectively. Numerical simulations were conducted by employing a geohydrological analysis of multiphase phase flow and thermal transport simulation of TOUGH2 (Pruess et al., 1999), and a rock and soil mechanics with hydromechanical and thermomechanical interactions computation of FLAC3D (FLAC3D, 2005). A 3D model of formations with the size of 3200 m ×3200 m and the depth of 1600 m was generated. The input of hydrological data of the model, including density, permeability, porosity, relative permeability data and capillary pressure were obtained from laboratory core tests. The rock formation was assumed to be homogeneous without fractures. Pore pressure, overburden pressure, and temperature were generated across the model in order to mimic the reservoir conditions.A CO2 injection well located at the centre of model surface, deeply down to the depth of 800 meters. The injection with the rate of 0.35kg/s was simulated over the injection period of 5, 10, and 25 years. The temporal -spatial stresses and strains in the model were examined. It was found that, over the same flow rate of injection, the uplift induced by CO 2 injection to Ainoura sandstone is higher than that to Berea sandstone. The increased pressure induced by CO2 injection into Ainoura sandstone was more pronounced at the vicinity of the injection point whereas the increased pressure induced in Berea sandstone was found to be more spreading from the injection point, even though it is very low due to low flow rate of injection. The increase of pressure altered the stress and strain in the rock formations, creating uplift in the overlying layers and subsidence in the underlyin g layers of the injection point. The uplift in the Ainoura sandstone maximized in a certain distance above the injection point and declines as it moves the surface. On the other hand, the uplift in Berea sandstone increased from the injection point to the surface. The uplift in Ainoura sandstone was higher than the uplift in Berea sandstone.The results also indicated that, the injection rate and permeability play important role in the pressure and ground deformation generated by injection. Overall, Berea sandstone performed a better storage capacity, yet it has poor in confinement. On the other hand, Ainoura sandstone showed well confinement but relatively poor storing capacity