三重介质低渗油藏非达西非稳态渗流研究

A study of non-Darcy transient flow in triple porosity media with low permeability reservoir

针对低渗透油藏不再符合线性达西定律的情况,考虑启动压力梯度和动边界共同影响,建立了带井筒存储和表皮效应的三重介质低渗油藏非达西非稳态渗流模型.鉴于数学模型的非线性和非齐次性,通过引入新定义的无量纲压力线性化压力扩散方程,采用Laplace变换结合Ste-hfest数值反演方法,研究了启动压力梯度、溶洞窜流系数、基质窜流系数、裂缝储容比和溶洞与基质储容比之比等敏感参数对无量纲井底压力和压力导数曲线的影响规律.结果表明:无量纲启动压力梯度为0时,压力导数具有无限大外边界的水平径向流特征,随着无量纲启动压力梯度的增大,压力导数曲线中后期上翘幅度越大.

Considering the combined influence of threshold pressure gradient and moving bound- ary, a model of non-Darcy transient flow in triple porosity porous media with effect of wellborestorage and skin effect was established for seepage does not obey linear Darey law low permeable reservoir. Due to the nonlinearity and nonhomogeneity of the mathematical model, La- place transform in combination with Stehfest numerical inversion algorithm was used to solve the model by introducing a new defined dimensionless pressure to the linearization of pressure diffusion equation. The research investigated the sensitive parameters, including threshold pressure gradient, rug interporosity flow coefficient, matrix interporosity flow coefficient, fracture storage ratio, the ratio of vug and matrix storage ratio, influencing on the dimensionless wellbore pressure and pressure derivative. The results show that there is horizontal radial flow with infinite outer boundary on the pressure derivative curve when the dimensionless threshold pressure is O; with the increase of the dimensionless threshold pressure, upwarp scope of the pressure derivative cure at the mid to late stage will tend to be an increase.