缝洞型碳酸盐岩油藏压力响应特征

Pressure response characteristics of fractured-vuggy carbonate reservoirs

缝洞型碳酸盐岩油藏开发过程中,由于部分储层中发育大尺度溶洞,溶洞的位置及大小将会影响储层中流体流动规律。在假设储层中大尺度溶洞为等势体、将基质和裂缝看作双重孔隙介质的基础上,建立了储层流动模型。采用Laplace变换和边界元方法对模型进行求解,得到了井底压力响应特征曲线。对比了双重孔隙介质模型的解析解与边界元方法的计算结果,证明了该模型的准确性。同时,对溶洞参数的敏感性进行了分析,分析结果表明:溶洞半径越大,特征导数曲线上上凸和下凹的幅度越大;压缩系数比越大,曲线上凸段持续时间越长,下凹幅度越大。该方法对发育大尺度溶洞的油气藏储量评估与地层测试有一定借鉴意义。

In the development process of fractured-vuggy carbonate reservoir, the location and size of cave will affect the fluid flow law. We take the large-scale cave as equipotential body, treat matrix and fracture as double porous media, and establish the flow model. Laplace transform is used to simplify the model, and then the model is solved using boundary element method. The results of analytical solution and boundary element method in the dual porosity medium show the accuracy of this model. The sensitivity of cave parameters is analyzed. It shows that the larger the cave radius is, the stronger the convex and concave of curve are. The segment of convex keeps longer and the concave margin is greater with the larger compressibility ratio. It has certain significance for the reserves evaluation and well test in this reservoir.