考虑基质收缩效应的复合煤层气藏产能评价

Production evaluation of coalbed reservoir with matrix shrinkage effect

目前大多数的煤层气藏产能评价软件都没有考虑基质收缩效应和体积压裂的影响。文中运用稳态扩散理论和达西定律,建立煤层基质的扩散方程以及天然裂缝系统的流动方程,再结合已有的基质收缩模型,得到考虑基质收缩效应和体积压裂影响的产能评价解析解。通过Duhamel褶积,实现了实际生产数据与理论模型的拟合,进一步实现了单井的产能评价和产能预测。通过引入稳态扩散理论和对应的拟时间函数,大大降低了复杂渗流规律及Duhamel褶积带来的巨大计算量,使得解析解的运算精度和速度达到了软件化的强度,实现了快速评价及准确预测气井产能的目的。文中所得的适用于煤层气藏压裂直井的产能评价方法,可为国内外煤层气藏开发及产能评价提供科学依据。

Since most current production evaluation models have not considered the matrix shrinkage effect and stimulated reservoir volume,the steady state diffusion and Darcy′s law are applied to construct the diffusion equation of matrix and the seepage equation of natural fracture system.Combined with different shrinkage models of the matrix,the analytical solution of production evaluation model that considers the effect of matrix shrinkage and stimulated reservoir volume is obtained.Using Duhamel convolution,the fitting of actual production data and theoretical model is realized,and the production evaluation and production prediction of single well are further achieved.By introducing the steady-state diffusion theory and the corresponding pseudo-time function,the huge amount of calculation caused by complexity of seepage flow and Duhamel convolution are greatly reduced.Consequently,the accuracy and speed of the analytical solution reach the strength of software implementation,achieving the goal of quick and accurate prediction of gas well production.Furthermore,a set of production evaluation methods suitable for the fracturing wells in coalbed methane reservoir is obtained,which provides the foundation of development of the domestic coalbed methane reservoir and the evaluation of coalbed methane reservoir involved in projects of international cooperation.