煤层气“甜点”测井判别与产量预测——以沁水盆地柿庄南区块为例

摘要

针对煤层气“甜点”判别与产量预测难的问题,提出了一种利用常规测井曲线评价煤层气“甜点”和产量预测的方法.以沁水盆地柿庄南区块3号煤层为研究对象,从煤层气单井平均日产气量入手,探讨不同单井平均日产气量煤层的敏感测井响应特征,利用井径、自然电位、自然伽马、深侧向电阻率和密度测井曲线,计算煤体结构指数、产能指数、含气量、含气饱和度、临界解吸压力及顶底板特性等煤层关键参数.综合煤体结构指数与产能指数构建了煤层品质参数,结合含气量、临界解吸压力与顶底板特性建立了柿庄南区块煤层气“甜点”测井判别标准;并利用煤层含气量、含气饱和度与产量刻度系数预测产气量,应用该方法处理解释研究区97口煤层气井,预测准确率达84％.%The paper introduces a method to solve the problems in sweet spot identification and production prediction in coalbed methane wells by using conventional well logging data.Taking No.3 coal seam in southern Shizhuang block of Qinshui basin as an example and starting from the average daily gas production in individual CBM wells,the paper discusses the logging response characteristics of the coal seam and calculates the key parameters of the coal seam such as coal texture index,productivity index,gas content,gas saturation,critical desorption pressure and coal roof & floor features by using caliper,natural potential,gamma-ray,deep lateral resistivity and density logging curves.The paper establishes a composite coal-seam quality parameter by using coal texture index and productivity index,builds up criteria to identify CBM sweet spot with logging data by integrating the composite quality parameter,gas content,critical desorption pressure and coal roof & floor features,and predicts CBM production by using gas content and gas saturation in coal seams,and production scale coefficient.The application results from 97 CBM wells in the study area show that the accuracy rate of the prediction method can reach 84％.