煤层气井优先抽排煤层上部含水层水的研究

Research on Water Draining Preferentially from Aquifer above Coal Seams in Coal-bed Methane Well Drainage

针对煤储层敏感性高和高产水、弱含水的储层特征,提出了一种新的排采方式,取得如下认识:1新排采方式优先抽排煤层上部承压含水层水,再进行煤层压裂、排采,确定了停止抽排含水层水的动液面高度;2该排采方式避免了部分常规排采方式存在的问题,包括吐砂、煤粉产出、气锁效应等,缩短了煤层气井排水周期;3新排采方式基于煤层之上有承压含水层的地层结构,对高产水井优势更大;4以柳林X1煤层气井为例,计算了应用新排采方式时,含水层排水阶段的临界动液面高度、降深和影响半径。

In order to solve the problems from high reservoir sensitivity and deal with the reservoir characteristic of high water production and low water content,a new drainage scheme is proposed,having following conclusions.Firstly,the scheme is draining away water in overlying aquifer before CBM well fracturing and mining. The critical dynamic liquid level for stopping pumping water from aquifer is provided. Secondly,it avoids many reservoir sensitivity problems,like sand and pulverized coal output and air lock effect and shorten the dewatering period of CBM recovery. Thirdly,the new proposal bases on the stratum structure of coal seam with aquifer above,and is more suitable for CBM well with high water production and long period of water producing. Fourthly,X1 CBM well in Liulin field is taken as an example,when using new drainage scheme,the critical dynamic liquid level,drawdown and influence radius is calculated.