稠油油藏化学降黏驱全耦合数值模拟方法

Full Coupling Numerical Simulation of Chemical Viscosity Reduction Flooding in Heavy Oil Reservoir

化学降黏驱是提高稠油采收率的新方法,现有的数值模拟方法不能准确描述降黏驱过程中各组分、相间的物理化学变化过程。结合油水两相控制方程、降黏剂浓度传质方程及辅助方程,构建了浓度场-渗流场全耦合化学降黏驱替数学模型,获得了乳液黏度-含水率、降黏剂溶液黏度-浓度及降黏剂溶液与原油界面张力的辅助方程,采用具有有界性的高阶迎风格式克服了一阶迎风格式的不足,提高了浓度散度的计算精度,优选有限体积方法提高了解的准确性,并对降黏驱数值模拟结果与实验结果进行了验证。在此基础上开展了降黏驱数值化实验,优化了降黏驱的注采参数。研究表明:建立的模型可以表征降黏剂的控黏效果;随着降黏剂注入浓度、注入量和注入速度的增加,采出程度逐渐增加,但采收程度增长率逐渐减小;0.4%浓度的降黏剂采收程度提高幅度最大;合理注入量介于0.2~0.6 PV,PV(pore volume)表示孔隙体积;推荐选用段塞较大、段塞中降黏剂浓度较高的方案;合理的注入速度应根据油田自身产能设计。该研究为稠油油藏降黏驱开发方式优化与调整提供了重要技术手段。

Chemical viscosity reduction flooding is a new method to improve heavy oil recovery.The existing numerical simulation methods can not accurately describe the physical and chemical changes of each component and phase in the process of viscosity reduction flooding.Combined with oil-water two phase control equation,viscosity reducer concentration mass transfer equation and related auxiliary equation,a fully coupled chemical viscosity reduction displacement model of concentration and seepage field was established.Viscosity concentration relations of viscosity reducer solution,the relationship of the moisture content emulsion viscosity and interfacial tension of crude oil and the viscosity reducer solution of auxiliary equation was got through physical model experiment.The high order upwind scheme with boundedness overcomes the deficiency of the first order upwind scheme and calculation accuracy of concentration divergence was improved.The finite volume method was preferred to improve the accuracy of solving.The results of numerical simulation and core displacement experiment were verified.On this basis,the numerical experiment of viscosity reducer flooding was carried out and injection and production parameters of viscosity reduction flooding were optimized.The results show that the established model can characterize the viscosity control effect of viscosity reducing agent.With the increase of viscosity reducing agent concentration,injection rate and injection speed,the recovery degree increases gradually while the growth rate of recovery degree decreases gradually.The increase degree of recovery is maximum with 0.4%concentration of viscosity reducing agent.Reasonable injection amount is ranged from 0.2 PV to 0.6 PV.The scheme with large slug and high viscosity reducing agent concentration in slug is recommended.The reasonable injection rate should be designed according to the field s own capacity.The study provides an important technical means for optimizing and adjusting the development mode of viscosity reduction flooding in heavy oil reservoirs.