煤层气水平井技术应用分析及优化

Application and optimization of CBM horizontal wells

全国主要煤层气区块15年以上的开发实践表明,不同地质条件下,相同的水平井技术开发效果差异较大,可复制性差,亟需进行技术优化。基于水平井技术应用典型案例的数据统计分析,研究了井型、井身结构、完井方式、储层强化技术、排采装备及工艺的优化方法。结果表明,井型和井身结构对煤层气高效经济开发起决定性作用。U型和L型水平井最具推广应用价值。井身结构优化应保持水平段井眼平滑,U型井水平段井眼下倾,L型井水平段井眼上倾且设置沉煤粉“口袋”。根据地应力、煤层埋深和渗透性选择完井方式,低地应力、埋深浅的高渗煤层,水平井段采用筛管完井;高地应力、埋深大的低渗煤层,水平井段采用“套管水泥固井+分段密集多簇射孔+大规模水力压裂”技术。排采设备优选“杆式泵+抽油机”组合,实施智能化、精细化排采,严格管控“上产—稳产”阶段的排液速率,保证水平井高产稳产。

The practical development experiences of CBM horizontal wells for more than 15 years in major CBM blocks of China shows that,there is wide variation in development effectiveness and poor repeatability among the same technology of horizontal wells under different geological conditions.Therefore,the optimal technology of horizontal wells needs to be further investigated.Based on data statistical analysis of typical application cases of CBM horizontal wells technology,the optimized methods of horizontal wells on the well types,the well structure,the completion method,the stimulation method and the drainage equipment and technology are studied.The results show that,the well type and well structure is decisive for efficient and economic CBM development.U-type and L-type wells have best potential for popularization and application.The optimization of horizontal well structure should keep the horizontal wellbore smooth,horizontal wellbore is down-dip for U-type wells,while it is up-dip and requires pocket for sinking coal powder in L-type wells.The completion method is selected according to the data of ground stress,depth and permeability of coal seam.The screen completion method should be adopted for lower ground stress,relatively shallow buried depth and high-permeable coal seam.Otherwise,the technology of“casing cementing+segmented dense multi-cluster perforation+large-scale hydraulic fracturing”should be adopted in the horizontal borehole.The match of rod pump and pumping unit is preferred as drainage equipment.The intelligent drainage and fine drainage should be implemented to strictly control the drainage rate of the uprising and stable stage of CBM production,thus to ensure the sustainable high production of CBM wells.