Geomechanical modeling for CO2 geologic sequestration in Asmari reservoir—south of Iran

Abstract

Due to releasing large amount of greenhouse gases in the atmosphere, some countries were committed to control the expansion of these gases into the environment. The best way to solve this issue is carbon capturing and sequestration (CCS). Injection of CO2 into the depleted reservoirs is one of the most favorite recommended solutions. Iran contains variety of depleted reservoirs. This makes good opportunity for geological sequestration of CO2. However, lack of caprock integrity may result in leakage of gas from the reservoir and could endanger the entire project and lead to serious problems. In this paper, a 3D reservoir and geomechanical models are built for a reservoir in Asmari formation that is sealed by Gachsaran-1 caprock. The parameters that are investigated in this challenging reservoir are vertical displacement of caprock, pore pressure changes, horizontal stresses changes, and finally caprock integrity during injection process. The caprock integrity has been studied by Mohr-Coulomb failure criterion, but we observed no failure. In addition, the variation of rock parameters such as poison ratio and young modulus was investigated on the integrity of caprock. The results illustrated that the caprock integrity in this reservoir is not significantly sensitive to above parameters. However, it is sensitive to the horizontal/vertical stress ratio changes. The increase of this ratio would increase the possibility of failure. The vertical displacement of caprock funds to be about 22 mm. The critical rate of CO2 injection is determined approximately 35.5 kiloton/month after 10 years of injection, which makes this reservoir a suitable option for the geological sequestration.