Optimization of Alternating Multi-thermal Fluid and Steam Huff and Puff for Enhancing Recovery in Overseas Extra-Heavy Oil Reservoirs

Under the “dual carbon” goals, multiple thermal fluid (MTF) simulation has been successfully applied in the overseas extra-heavy oil M oilfield of CNPC. However, the MTF exhibits low enthalpy per cycle, and the number of annual huff and puff operations is limited. To fully exploit the advantages of MTF and further enhance extra-heavy oil thermal recovery, this study innovatively proposes an optimization of alternating MTF and cyclic steam simulation (CSS). Twenty-one numerical simulation schemes of alternating MTF and CSS are designed. By establishing an actual well-group model of the overseas extra-heavy oil M oil field, the influences of factors-such as alternation mode and alternation timing-on development effect are simulated. The optimal alternation mode is identified as: two cycles of CSS followed by one cycle MTF. This approach can increase the well-group recovery by 3.7% during the huff and puff stage. The optimal timing of alternation implementation is after two cycles of CSS. The research results have been successfully implemented in overseas extra-heavy oil field, yielding significant improvements: oil-steam ratio increased by 0.4, cyclic oil production increased by 618t, water cut decreased by 10%, huff and puff duration extended by 100 days, cyclic steam injection volume reduced by 1838t. The alternation mode innovatively proposed in this study has guiding significance for improving the thermal recovery performance and enhancing recovery rate in overseas extra-heavy oil fields.