Exsolution Enhanced Oil Recovery with Concurrent CO2 Sequestration

A novel EOR method using carbonated water injection followed by depressurization is introduced. Results from micromodel experiments are presented to demonstrate the fundamental principles of this oil recovery method. A depressurization process (1 MPa/hr) was applied to a micromodel following carbonated water injection (Ca ≈ 10-5). The exsolved CO2 in water-filled pores blocked water flow in swiped portions and displaced water into oil-filled pores. Trapped oil after the carbonated water injection was mobilized by sequentially invading water. This method's self-distributed mobility control and local clogging was tested in a sandstone sample under reservoir conditions. A 10% incremental oil recovery was achieved by lowering the pressure 2 MPa below the CO2 liberation pressure. Additionally, exsolved CO2 resides in the pores of a reservoir as an immobile phase with a high residual saturation after oil production, exhibiting a potential synergy opportunity between CO2 EOR and CO2 sequestration.