注水开发油藏润湿性变化及其对渗流的影响

为提高水驱开发油藏采收率预测精度,研究了油藏岩石润湿性与相对渗透率之间的变化规律及其对两相渗流的影响。采用室内润湿性实验测定方法,对水驱开发油藏润湿指数与含水饱和度的关系进行了定量表征,导出了适合润湿性变化型油藏的两相渗流方程,建立了变润湿性水驱开发油田的采收率预测方法。润湿实验结果表明:所测岩心的润湿指数的对数与取心油层的含水饱和度呈近似线性关系。相对渗透率实验所测的代表低含水期到高含水期岩心的油水两相等渗点对应的含水饱和度由41%增加到53%,亲水程度增强。一维模型计算结果表明,含水率达到98%时,油润湿和强水润湿性油藏的预测采收率分别为52.7%和73.3%。研究揭示的水驱油藏岩石润湿性变化规律和建立的数学模型,可为更加准确地预测水驱油采收率提供参考。

Wettability Change and Its Effect on Flow in Waterflooding Reservoirs

To improve the prediction accuracy of the oil recovery by waterflooding,the changes in wettability and relative permeability of reservoir rocks and their effects on two-phase flow had been researched.Wettability experimental measurements and applied mathematics were conducted to characterize the correlation between the wettability of reservoir rocks and water saturation during waterflooding.The governing equations of two-phase flow were derived to fit wettability changes in oil reservoirs.And the prediction method of oil recovery with wettability variation in waterflooding of oil fields was presented.Wettability experimental results showed that the relation between the logarithm of wetting index and water saturation of sandstone cores was approximately linear.Relative permeability experimental results showed that water saturation for the equal values of water and oil relative permeabilities increases from 0.41 to 0.53 in the cores from low water-cut to high water-cut reservoirs,which also indicated the rise in water wettability.Simulation results of one dimensional model showed that the predicted oil recoveries for oil and water wetting reservoirs were 52.7% and 73.3%,respectively.The wettability variation trend and mathematical model presented in this paper lay theoretic foundation for accurate prediction for oil recovery by waterflooding.