Analysis of the effect of formation dip angle and injection pressure on the injectivity and migration of CO2 during storage

Carbon dioxide (CO2) geological storage (CGS) can help realize the plan of “Carbon Neutrality”. Injection capacity and storage safety are crucial factors in evaluating CO2 storage efficiency. Deep saline aquifers are major sites for CGS. This study focused on evaluating the CO2 injection amount, migration safety and leakage risk. A three-dimensional (3D) model of the Shenhua CO2 capture and storage (CCS) project in the Ordos Basin, China, was established to discuss the impact of injection pressure (1.3P (equal to 1.3 times the top reservoir formation hydrostatic pressure), 1.4P, and 1.5P) and formation dip angle (0°, 5°, 10°, 15°) with fault on the total CO2 injection and migration safety. Twelve schemes were designed for simulation. Based on the results, faulting provided a pathway for CO2 leakage, posing a threat to CO2 storage safety. Injection pressure and formation dip angle had significant effects on injectivity and migration during CO2 storage. The influence of the injection pressure on the CO2 injection amount was more evident than that of the dip angle, though formation dip angle had a significant impact on the CO2 migration during storage. Increasing the injection pressure and formation dip angle increased the gas and dissolved-phase CO2 migration and decreased the CO2 leakage time and storage safety. The CO2 leakage through the fault occurred after 160, 110 and 80 years in a 15° sloping formation with 1.3P, 1.4P, and 1.5P, respectively. The CO2 injection amount was the largest for the 0° formation with 1.5P. These results provide fundamental information for CO2 storage safety and capacity, suggesting that un-faulted reservoirs with smaller dip angles should be selected for CGS projects; however, larger injection pressures can result in greater injection amounts, decreasing the migration safety of CO2 during storage.