煤层气羽状水平井数值模拟新方法

A NOVEL METHOD FOR NUMERICAL SIMULATION OF FISHBONE WELL PERFORMANCE IN COALBED METHANE RECOVERY

羽状水平井技术是近几年兴起的一项新的煤层气增产技术。目前,在煤层气数值模拟中广泛采用的笛卡儿正交网格,在描述羽状水平井等复杂井型方面存在较大的局限性,并且在模拟过程中存在严重的网格取向效应。针对这一问题,提出使用笛卡儿网格和六边形PEBI网格分别对羽状水平井和煤层气藏区域进行模拟的混合PEBI网格模拟方法;给出了控制体有限元差分方程,提出了新的混合网格生成方法;结合某煤层气田实际地质资料,对直井、水平井和羽状水平井等开发方式分别进行了模拟。计算结果表明,该网格系统节点灵活,能够广泛适用于多种井型的煤层气数值模拟。

In recent years, application of fishbone horizontal wells in enhancing the recovery of coalbed methane is becoming more and more popular. The coordinate system used widely now for numerical simulation is Cartesian coordinate, which has obvious limitations by the description of such complex wells as fishbone and also has severe grid orientation effect during the simulation process. Aiming at these problems, this study presented a blended PEBI network, using Cartesian network and hexagonal PEBI network to represent the gas reservoir region and the surrounding region of the wellbore. This study also described correspondent finite difference equations and the method to develop such blended grid system. According to the simulation results of this new method for vertical, horizontal and fishbone wells, this paper concludes that this blended PEBI network has great flexibility as to grid nodes and can be applied for simulation of different well types in coalbed methane reservoir.