Oil recovery enhancement in low permeable and severe heterogeneous oil reservoirs via gas and foam flooding

In view of the co-existence of the low permeability and severe heterogeneity, the effective tertiary technique for the enhanced oil recovery is still in progress. In this study, on the base of the simulation of SH reservoir conditions, we conducted the trinal-core flooding experiments about gas flooding (N-2 and CO2), WAG (N-2 and CO2) injection and foam flooding (N-2 and CO2). Combined with some static investigations, we found that CO2 flooding achieves additional oil recovery due to the development of near-miscibility and CO2 extraction, and the WAG injection can relieve the gas channeling associated with gas flooding. As for the foam flooding, CO2 foam has the advantage of oil displacement in a higher permeability layer and nitrogen foam is capable of diverting the flow to the least permeability zone in the strong heterogeneity formation and sharply increasing the oil recovery. It is also found that, in the pilot test of SH reservoir, nitrogen foam flooding is qualified for flow adjustment, water controlling and oil recovery enhancement in the low permeable and severe heterogeneous reservoir.