CO₂ immiscible flooding is an environmentally-friendly and effective method to enhance oil recovery in ultra-low permeability reservoirs. A mathematical model of CO₂ immiscible flooding was developed, considering the variation in crude oil viscosity and starting pressure gradient in ultra-low permeability reservoirs based on the non-Darcy percolation theory. The mathematical model and numerical simulator were developed in the C++ language to simulate the effects of fluid viscosity, starting pressure gradient, and other physical parameters on the distribution of the oil pressure field, oil saturation field, gas saturation field, oil viscosity field, and oil production. The results showed that the formation pressure and pressure propagation velocity in CO₂ immiscible flooding were lower than the findings without considering the starting pressure gradient. The formation oil content saturation and the crude oil formation viscosity were higher after the consideration of the starting pressure gradient. The viscosity of crude oil considering the initiation pressure gradient during the formation was higher than that without this gradient, but the yield was lower than that condition. Our novel mathematical models helped the characterization of seepage resistance, revealed the influence of fluid property changes on seepage, improved the mathematical model of oil seepage in immiscible flooding processes, and guided the improvement of crude oil recovery in immiscible flooding processes.

CO ₂非混相驱是一种环境友好、有效的特低渗透油藏提高采收率方法。基于非达西渗流理论，建立了考虑超低渗透油藏原油粘度变化和启动压力梯度的CO ₂非混相驱数学模型。采用C++语言开发数学模型和数值模拟器，模拟流体粘度、启动压力梯度等物理参数对油压场、含油饱和度场、含气饱和度场、油粘度场和油层分布的影响。石油生产。结果表明，CO ₂非混相驱地层压力和压力传播速度均低于未考虑起始压力梯度的计算结果。考虑启动压力梯度后地层含油饱和度和原油地层粘度较高。考虑形成过程中起爆压力梯度的原油粘度高于无起爆压力梯度条件下的原油粘度，但产量低于无此梯度条件下的原油。新颖的数学模型有助于表征渗流阻力，揭示流体性质变化对渗流的影响，完善非混相驱过程中石油渗流的数学模型，指导非混相驱过程中原油采收率的提高。