Challenges in Modeling Coupled Thermo-Hydro-Mechanical-Chemical Processes for CO₂ Injection in a North Sea Hydrocarbon Chalk Reservoir

CO₂ injection in depleted oil and gas reservoirs has become increasingly important as a means of mitigating greenhouse gas emissions. This study investigates coupled multiphysics simulations of CO₂ injection in chalk reservoirs to better understand the complex thermo-hydro-mechanical-chemical (THMC) processes involved. Two compositional models are created: an isothermal model and a non-isothermal model. Since temperature impacts on fluid compositions have introduced errors in estimating the reservoir's compositions, we made certain simplifications on fluid compositions for the thermal model to address this issue. By using the simplified model, we simulate the temperature propagation of cold fluid into a hot reservoir to observe induced thermal stress due to temperature changes. Despite these simplifications for geomechanical modeling, the propagation of CO₂ in the depleted gas reservoir was calculated without considering thermal effects, assuming that the density and viscosity of CO₂ remained constant with temperature change in the coupled simulation. Our findings provide valuable insights into the THMC processes involved in CO₂ injection in the depleted gas reservoir and highlight the importance of accurately modeling thermal effects to improve simulation accuracy.