大宁-吉县区块8号煤裂缝三维特征评价及压裂段优选

Evaluation of 3D characteristics and optimization of fracturing sections for No.8 coal seam crack in Daning-Ji County block

煤岩储层具有典型的双重孔隙结构,裂缝的发育影响煤层气储集、扩散和渗流,也是煤岩储层压裂改造评价的一项重要参考。目前研究裂缝的常规方法在岩心裂缝三维精细表征上均有不足,采用全直径CT扫描技术对大宁-吉县区块9口井煤岩裂缝进行精细三维刻画。测试结果表明,研究区太原组中浅层8号煤岩和深层8号煤岩裂缝特征差异明显,中浅层煤岩裂缝更发育,深层煤岩裂缝充填率更高。中浅层煤岩平均总裂缝率5.25%,裂缝充填率37.1%,常见高角度缝和水平缝,深层煤岩平均总裂缝率4.47%,裂缝充填率达到50.3%,端割理发育且多被矿物充填,在三维形态上呈复杂的网状。通过多维度定量化参数对研究区煤岩储层裂缝进行评价,划分了3个级别,为单井煤岩压裂段优选提供有利依据,现场应用于H15井压裂试气,取得了良好的效果。研究成果可为下一步区内井位试气选层和实施不同层位勘探开发方案提供技术支撑。

Coal rock reservoirs have a typical dual pore structure,and the development of fractures affects the storage,diffusion,and seepage of coalbed methane.It is also an important reference for the evaluation of coal rock reservoir fracturing and transformation.At present,the conventional methods for studying fractures are insufficient in the 3D fine characterization of core fractures.Full-diameter CT scanning technology was used to accurately depict coal and rock fractures in 9 wells in the Daning Ji County block.The test results showed that there was a significant difference in the characteristics of fractures between the middle-shallow and deep No.8 coal rocks in Taiyuan Formation of the study area.The fractures in the middle-shallow coal rocks were more developed,and the filling rate of fractures in the deep coal rocks was higher.The average total fracture rate of middle-shallow coal rocks was 5.25%,with a fracture filling rate of 37.1%.High angle and horizontal fractures were common,while the average total fracture rate of deep coal rocks was 4.47%,with a fracture filling rate of 50.3%.The end cutting was developed and often filled with minerals,presenting a complex network in 3D morphology.The evaluation of coal rock reservoir fractures in the study area was conducted through multi-dimensional quantitative parameters,and three levels were divided,providing a favorable basis for the optimization of single well coal rock fracturing sections.The on-site application in H15 well fracturing and gas testing achieved good results.The research results can provide technical supporting for gas testing and layer selection at the next well location in the area,as well as for implementing exploration and development plans for different layers.