一种新的非线性渗流数值模拟模型

A new nonlinear seepage numerical simulation model

针对当前数值模拟软件只能近似等效模拟启动压力梯度,且模拟结果准确性不高等问题,为了准确描述流体在多孔介质流动时视黏度的变化规律,引入了油相视黏度与流动修正系数,建立了可模拟稠油非线性渗流特征的新型数值模型。研究结果表明:(1)新模型将非牛顿流体与牛顿流体渗流规律的不同转变为由于流动修正系数的不同造成的,当流动修正系数变为1时,该方程就退化为牛顿流体的方程形式;(2)通过对日产油、地层压力、含水率等开发指标预测对比发现,2种模型预测结果趋势基本一致,验证了模型的稳定性和准确性;(3)利用机理模型对渗透率级差、原油黏度、井网形式、井距以及采液速度开展单因素分析,结果表明存在启动压力梯度时,会对水驱油过程产生一个附加渗流阻力,致使驱替过程非活塞现象严重,驱油效率降低,波及范围减少,层间矛盾突出,采出程度下降,含水率上升,开发效果变差。

Aiming at the problem that the current numerical simulation software can only approximately simulate the starting pressure gradient and the accuracy of the simulation results is not high,in order to accurately describe the change law of apparent viscosity of fluid in porous media flow,the oil apparent viscosity and flow correction coefficient are introduced,and a new numerical model is established to simulate the nonlinear seepage characteristics of heavy oil.The research results show that:(1)The new model transforms the difference of seepage law between non-Newtonian fluid and Newtonian fluid into the difference of flow correction coefficient.When the flow correction coefficient becomes 1,the equation degenerates into the equation form of Newtonian fluid;(2)Through the prediction and comparison of development indicators such as daily oil production,formation pressure and water content,it is found that the prediction results of the two models are basically consistent,which verifies the stability and accuracy of the model;(3)The mechanism model is used to carry out the single factor analysis on the permeability gradient,crude oil viscosity,well pattern,well spacing,and liquid production rate.The results show that when there is a starting pressure gradient,an additional seepage resistance will be generated in the water flooding process,resulting in serious non-piston phenomenon in the flooding process,reduced oil displacement efficiency,reduced sweep range,prominent interlayer contradictions,reduced recovery degree,increased water content,and poor development effect.