含大尺度溶洞的缝洞型油藏压力瞬变分析及溶洞体积反演

Pressure transient analysis and inversion of vug volume of fractured vuggy reservoirs containing large-scale vug

文章建立一个适用于解释含大尺度溶洞的缝洞型油藏试井模型。首先推导出包含大尺度溶洞情况下井筒与溶洞压力之间的关系,将其作为内部控制方程,然后将外地层简化为双重介质,引入渗流方程作为外部控制方程,再将内、外部控制方程相结合,给定边界条件,采用Laplace变换求解出井底压力解;根据井底压力解画出典型曲线,将流体在该类油藏中的流动分为5个流动段;对各个影响参数进行敏感性分析;通过参数反演得到大溶洞高度、半径、体积参数。以1口实例井为例,展示该文模型的具体应用,得到的参数与实际地质数据较为符合,验证了该模型的正确性。

In this paper,a new well test model applicable for the fractured vuggy reservoirs containing large-scale vug is established.First,the pressure difference between the wellbore and vug is derived and regarded as the internal governing equation.Then,the outer formation is simplified as a dual medium,and the seepage equation is introduced as the external governing equation.Through the Laplace transform,the analytical solution of bottom-hole pressure can be obtained with given boundary conditions.According to the solution,a typical curve of bottom-hole pressure can be drawn,the fluid flow in this kind of reservoir can be divided into five regimes.Then the sensitivity analysis of each parameter is carried out,and the influence of different parameters can be obtained.Meanwhile,the height,radius and volume of large vug can be obtained.Finally,an example well is given to demonstrate the application of the proposed model.The obtained parameters are in good agreement with the geological conditions,and the accuracy of the proposed model is verified.