Abstract: In the late stage of steam huff and puff or steam flooding for the heavy oil reservoir, the oil-steam ratio is only 0.1 to 0.2, which leads to high energy consumption and carbon emissions. To address the issue, a recovery method that utilizes low-viscosity oil injection assisted heavy reservoir with gas huff and puff has been proposed to improve the development effect. Through indoor test and reservoir numerical simulation, the mechanism and applicability are studied, and the technical boundary are delimited. The study shows that the mechanism of heavy reservoir with gas huff and puff assisted by low-viscosity oil injection is mainly viscosity reduction by dilution, solution gas drive, swept volume expansion and facies change by emulsification. The oil-carrying rate (volume ratio of produced heavy oil to injected low-viscosity oil) can reach 1.00-3.00, and the energy consumption and the water production is low. The new method is suitable for conventional heavy oil reservoirs and extra-heavy oil reservoirs, especially for deep zones, thin interbedded and small fault blocks. This study has guiding significance for reservoir screening and engineering design of heavy reservoir with gas huff and puff assisted by low-viscosity oil injection.

Key words: low viscosity oil, gas, huff and puff, heavy oil, low carbon, oil-carrying rate