Addressing mobility control challenges in high-pressure high-temperature oil reservoirs via water-saturated CO2 injection

The ability of pure CO2 injection into an oil reservoir to bring about CO2 storage is hindered by the fact that CO2 is more mobile than oil. Most "mobility control" methods (such as foam injection) work only at low temperatures. This study investigates whether water-saturated CO2 injection can provide mobility control at high pressures and temperatures. In this study, CO2 and water-saturated CO2 are injected into a Bentheimer sandstone core. Experimental runs are performed at 70 ◦C to simulate a low-temperature reservoir and 116 ◦C to simulate a high-temperature reservoir. The selected pressure ranges from 10.3 to 18.6 MPa. Results show that water-saturated CO2 consistently exhibits lower mobility than pure CO2 . Hence, water-saturated CO2 injection provides effective mobility control for both low- and high-temperature reservoirs, especially at higher pressure. The effectiveness of water-saturated CO2 in reducing mobility compared to pure CO2 increases exponentially with pressure. Despite the improved mobility control provided by watersaturated CO2 injection, experimental observation finds net CO2 stored and oil recovery to be similar to that of pure CO2 injection,as CO2 sweep efficiency is already high in experimental runs. However, at field-scale sweep efficiency is low. Therefore, field-scale simulations reveal a 19%-47% increase in net CO2 stored during water-saturated CO2 injection compared to pure CO2 injection. Document Type: Original article Cited as: Yin, H., Ge, J., Hussain, F. Addressing mobility control challenges in high-pressure high-temperature oil reservoirs via water-saturated CO2 injection. Advances in Geo-Energy Research, 2025, 16(3): 276-287. https://doi.org/10.46690/ager.2025.06.07