Coupled Hydraulic and Mechanics Finite Element Modeling of CO2 Injection into a Layered Isotropic Media Using FEHM

Abstract

CO2 injection into the hydrocarbon reservoir affects the subsurface mechanics and hydraulic condition. The injection has to be performed in a way that there will be no reservoir and/or top seal failure. In such case, a simulation of the injected fluid propagation needs to be performed to see its possible impact to the top seal and existing major faults. We use finite element method to perform this injection simulation. In this research, we use open source software Finite Element Heat and Mass Transfer Code (FEHM) to simulate CO2 injection processes into reservoir. Subsurface geological model was constructed in a dimension of 3000 m (easting) x 3000 m (northing) x 2000 m (vertical). Vertically, it consists of four layers which represent upper layer (400 m), top seal (200 m), reservoir (900 m), and basement (500m). The grid around the reservoir rocks is refined to give more detail results. The open hole injection is set at 850 - 890 m depth, 1500 m easting and 1500 m northing. The material is assumed to be isotropic. The initial pressure and temperature increase as a function of depth with a pressure gradient of 0.00981 MPa/m and a temperature gradient of 0.025 degrees C/m. A vertical fault is modelled at 600 m eastern to the injection well. Injection process is carried out with 6 kg/s of CO2 injection with simulation time for ten years to see its impact to the fault. A vertical fault is The modelling results show that the CO2 injection will not reactivate the fault at 10 years.