沁水盆地南部煤层气水平井射孔优化

Optimization of Perforation in CBM Horizontal Wells in Southern Qinshui Basin

为提高沁水盆地煤层气水平井压裂效果,基于分布式光纤水平井产水产气剖面监测、水平井录井导向、测井等资料分析,明确了煤岩煤质、煤体结构、水平井钻遇位置以及射孔改造方式是决定煤层压裂改造效果的关键因素。沁水盆地3号煤层中—上部自然伽马低、煤质较好、煤体结构完整,是适合压裂改造的优质层段;根据双自然伽马曲线可准确判断水平井井眼轨迹在煤层中的钻遇位置,确定优质压裂层段及射孔方式。当井眼轨迹位于煤层中部时,采用常规射孔方式可实现高效改造;当井眼轨迹接近顶板或出层时,需采用向下定向射孔方式,实现上部优质煤层的有效改造;当井眼轨迹位于下夹矸层附近时,可采用向上定向射孔方式,实现中部优质层段的改造。该方法现场应用水平井46口,单井日产气量突破2.5×10^(4)m^(3),日稳产气量达到2×10^(4)m^(3),储集层压裂改造效率提升10%~50%,水平井开发效果好。

To enhance the fracturing performance of coalbed methane(CBM)horizontal wells in the Qinshui basin,by analyzing the data of distributed optical fiber monitoring of water and gas production profiles,mud log,and well logging,the key factors influencing the fracturing performance were identified.These factors include coal quality,coal structure,drilling position,and perforation method.The middle to upper part of coal seam No.3 in the Qinshui basin,characterized by low GR values,high coal quality,and intact coal structure,is identified as the optimal interval for fracturing stimulation.Based on the double GR curves,the drilling position of horizontal wellbore trajectory in the coal seam can be accurately determined,aiding in the selection of optimal fracturing interval and perforation method.When the drilling position is located in the middle part of the coal seam,conventional perforation method can be efficient.When the drilling position approaches the roof or is beyond the seam,downward directional perforation is preferred to effectively stimulate the high⁃quality upper part of the coal seam.When the drilling position is near the lower dirt band,upward directional perforation is advisable to target the high⁃quality middle part of the coal seam.Field application to 46 horizontal wells demonstrated that the single well production exceeded 2.5×10^(4)m^(3)/d and was stabilized at 2×10^(4)m^(3)/d,and the reservoir fracturing efficiency increased by 10%to 50%,recording a satisfactory development effect of the horizontal wells.