Comprehensive Stress Sensitivity Analysis During CO2 Flooding and Storage in Tight Sandstone Reservoirs

Abstract Understanding the influence of CO2 injection on rock stress is one of the key elements to analyze CO2 Enhanced gas recovery and long-term CO2-storage in tight sand gas reservoirs. Producing natural gas from a reservoir and injecting CO2 to the tight reservoir causes a change in pore pressure, which in turn, changes the three-dimensional effective stress state that can result in reservoir rock deformation and permeability changes. In order to depict these effects, a new experiment and modeling method for CO2 flooding, considering the interaction between CO2 and rock is required. This paper presents a series of stress-sensitive experiments during CO2 flooding. A total of twenty sandstone rock samples, which include sandstones with natural fractures, shear fractures and artificial sanding crack fractures, were selected to study stress-sensitivity during gas production and CO2 flooding. Core flooding experiments were conducted using the following flow regime: depletion followed by CO2 injection. numerical simulations coupled with nonlinear geo-mechanic model with fluid flow were performed using the experimental data. The simulation results give a detailed understanding of the experimental geo-mechanic system. It is concluded that the experimental and simulation methods can be used in combination to evaluate the potential for stress changes during CO2 flooding in tight gas reservoirs. The results show that the evolution of the stress state, captured as a stress path, significantly affects the gas production profile and CO2 storage capability.