一种致密气藏生产动态分析新方法

A Novel Dynamic Analysis Method of Shale Gas Reservoir

致密气藏常采用多段压裂水平井技术进行储层改造以实现商业开发,目前主要有三种致密气藏动态分析方法:解析法、半解析法和数值模拟法。解析法和半解析法运算速度较快但仅适用于均质储层,数值模拟法可以准确地计算非均质储层的复杂几何形状井(如压裂水平井)但费时费力。为提高致密气藏动态分析的准确性和高效性,提出一种针对致密气藏压裂水平井的动态分析半解析新方法,即快速推进法(Fast Marching Method,简称FMM)。首先考虑气体的高度压缩特性,建立致密气扩散方程。然后根据快速推进法求解压力波的传播时间,进一步结合几何近似法量化泄气体积随时间的变化关系。接着采用商业数值模拟软件CMG验证了新方法的准确性和可靠性,结果表明,基于快速推进法的动态分析方法比常规动态分析方法准确,比商业软件计算速度提升了10%以上。最后阐述了快速推进法开展致密气藏压裂水平井动态分析的工作流程。快速推进法对构造条件简单的致密气藏生产动态分析,具有很好的应用价值。

In order to realize commercial development, multi-stage fracturing and horizontal well technologies are often used in tight gas reservoir. At present, there are mainly two methods for tight gas reser-voir performance analysis: analytical method and numerical simulation method. The analytical method is fast, but it is only suitable for homogeneous reservoir. The numerical simulation method can accurately calculate complex geometry wells (such as fractured horizontal wells) in heteroge-neous reservoir, but it is time-consuming and laborious. In order to improve the accuracy and effi-ciency of dynamic analysis of tight gas reservoir, a semi analytical method for dynamic analysis of multiple fractured horizontal wells in tight gas reservoir, namely fast marching method (FMM) is proposed. Firstly, considering the high compressibility of gas, the diffusion equation of tight gas is established. Then, fast marching method is proposed to solve the propagation time of pressure wave, and combined with the geometric approximation method, the relationship between the re-lease volume and time is quantified. Then, the commercial numerical simulation software CMG is used to verify the accuracy and reliability of the new method. The results show that the dynamic analysis method based on fast marching method is more accurate than the conventional dynamic analysis method, and the calculation speed is increased by more than 10% compared with the commercial software. Finally, the working process of fast marching method to carry out the dynamic analysis of fractured horizontal wells in tight gas reservoirs is described. It has good application value for the dynamic analysis of tight gas reservoirs with simple structural conditions.