Optimization of Each Component Ratio of Multiple Thermal Fluids in Extra-Heavy Oil Reservoir

Under the goal of “carbon peaking and carbon neutrality”, the technology of multiple thermal fluids is widely used to develop heavy oil reservoirs at home and abroad for its advantages of low carbon and environmental protection. The multicomponent thermal fluids mainly contain nitrogen, carbon dioxide and steam. In the formation, multi-components play an important role in the huff and puff effect. In order to improve the development effect of extra-heavy oil reservoir, the optimization of each component ratio must be further studied. Based on the single factor analysis method and orthogonal test method, this paper designs 40 groups of multi-component thermal fluids numerical simulation schemes with different component proportions. CMG software simulates the influence of steam injection rate, gas-steam ratio, CO₂-N₂ ratio and other injection parameters on the development effect of multi-component thermal fluids. The results show that the ratio of CO₂ to N₂ is the significant factor affecting the huff and puff effect, and the sensitivity order is CO₂ to N₂ ratio, gas-steam ratio and steam injection rate. The optimal injection parameter combination is as follows: the steam injection rate is 200 t/d, the gas-steam ratio is 300 m³/t, and the ratio of CO₂ to N₂ is 70%:30%. Viscosity deduction of muti-component thermal fluids has two regions: high temperature viscosity reduction and CO₂ dissolution viscosity reduction region. The results of this study have theoretical guiding significance for the optimization of injection-production parameters of multiple thermal fluids huff and puff, and can be further applied to field practice.