贵州煤层气新井压降测试分析

Pressure-drop Testing of A New CBM Well, Guizhou Province

准确获取煤层的渗透率、地层压力以及煤层的破裂压力和闭合压力等储层参数,是为下步增产措施和进一步评价该地区煤层气勘探开发前景提供依据的重要环节。为此分析了某矿区A井(新井)3号煤层注入压降测试和原地应力测试数据,通过双对数曲线、霍纳曲线以及压力拟合求取煤层参数,并用半对数曲线加以验证;在原地应力测试阶段通过时间平方根曲线分析求取储层的破裂压力和闭合压力等地层参数。结果表明:3号煤岩层渗透性较差,属于高压煤层,井筒储集系数较小,采用井下关井方式降低了井筒储集效应对测试数据分析的影响,井筒附近煤层完善程度较好,地应力梯度正常。

Getting right parameters of a coal reservoir, including permeability, formation pressure, and breakdown and closure pressure, is important to making stimulation measures and evaluating exploration and development prospect of CBM. No.3 coal bed from A well in a certain mining area was taken as an example. Some data from injection pressure-drop testing and in-situ stress testing were analyzed; and then, obtained by log-log curves, Horner Plot,and pressure matching, some parameters could be confirmed by semi-log curves; finally, such formation parameters as breakdown and closure pressure were acquired by a square-root curve. Results show that this coal bed is characterized by poor permeability, high pressure, and small reservoir coefficient. To adopting a way of downhole shut-in may reduce the reservoir effect on testing data. In addition, this bed is in good condition near wellbore and its stress gradient is also normal.