韩城矿区煤层气井试井分析

Analysis of CBM Well Test in Hancheng

注入/压降试井是确定中国中高煤阶煤层气渗透率的主要手段,具有重要意义。本文以无限大边界定产微分方程组为基础,在限定微分方程近似解所需要满足的假设条件基础上,详细推导了注入/压降试井求取渗透率等地层参数的公式。依据物质平衡原理,通过时间转化将多排量试井等效为单排量试井,使压力恢复试井法能够解决多排量试井问题,精度高。对韩城矿区试井资料、生产资料进行分析,求取了煤层的渗透率、原始地层压力、每米吸水指数等参数。煤层的渗透率普遍小于0.1×10-3μm2,含气饱和度低。把试井结果对比分析,吻合程度较高,试井结果可以作为求取煤层渗透率参数的一个重要依据。

Injection / fall well test is the primary means to obtain the permeability of Chinese high- rank coal,as is of great significance. Based on the differential equations on the conditions of infinite boundary constant production,with the restraining of the assumptions,a detailed formula is derived to describe formation parameters（ permeability for instance）. With the material balance principle,the multi- displacement well test is equivalent to a single displacement by the transformation of time. Thus the pressure build- up test method can solve the problem of multi- well test displacement with a high accuracy. According the datas of well test and production in Hancheng,parameters are obtained such as the permeability of the coal seam,the original reservoir pressure and the injectivity index per meter. Permeability of coal seam is generally less than 0. 1 × 10- 3μm2,and the gas saturation is low as well.Comparing with the well- test results,a high degree of agreement appeared. And therefore the well test results can be used as an important basis for obtaining coal seam permeability parameters.