沁水盆地柿庄区块煤层气井压裂增产效果关键影响因素分析与实践

Analysis and application of key influencing factors of CBM well fracturing effects in Shizhuang area, Qinshui basin

针对沁水盆地柿庄区块煤层气开发过程中低产低效问题,基于大量实际生产资料分析,探讨地质因素和工程因素对煤层气开发效果的影响。结果认为,地应力和煤体结构是影响煤层气井压裂增产效果的关键地质因素。其中,煤层气井压裂过程中,高地应力影响裂缝延伸和支撑,水平主应力差影响裂缝延伸方向和形态;煤体结构较差的煤层在压裂中易形成煤粉,堵塞导流通道,压裂效果变差。影响压裂效果的工程因素主要包括压裂液性能、施工排量、前置液占比和井径扩大率,针对研究区地质概况,提出“2%KCl+清水、阶梯排量注入、前置液量180~240m^3、优化射孔段和水力波及压裂”等系列优化技术,并指出煤层气压裂选井是决定压裂效果和开采经济性的重要环节。将优化技术在柿庄区块北部深部煤层气开发井中加以实践验证,取得很好的增产效果。研究成果及认识对沁水盆地及相同地质条件区域的煤层气开发具有一定的指导意义。

CBM fracturing effect has many influencing factors.Development effect with the same technology is different in different area.Based on a large amount of geological and engineering data in Shizhuang block,it was found that high geo-stress affects fracture extension and support in CBM fracturing,and difference between horizontal stress affects fracture direction and morphology.Coal seam with poor coal structure can produce large amount of gum during fracturing,which will block the diversion channel and result in poor fracturing effect.Engineering factors affecting fracturing effect mainly include the fracturing fluids performance,displacement,prepad fluid proportion and hole enlargement ratio.Finally,a serie of optimized technique was proposed,including “2%KCl+water,ladder displacement injection,prepad fluid volume 180-240 m3,perforation optimization and hydraulic networks fracturing”.It was pointed out that the well pattern of CBM fracturing was important to fracturing effects and economics.Field practice shows that the research results have strong guiding significance for CBM development.