煤层气水平井筛管密集分段径向射流增透方法

Dense segmented radial jetting stimulation method of screen tube in coalbed methane horizontal well

水平井煤层伤害后渗透性差、常规分段水力射流间距长,为提高近井壁煤层渗透性,优化设计了弹簧-液压式封隔器与注液短节,提出了以筛孔为喷嘴的煤层气水平井筛管密集分段径向射流增透方法。建立了单个筛孔径向射流破岩计算模型和近井壁煤岩增透渗流增量比计算模型,优化设计了筛管孔密、筛孔出口流速和射流排量,分析了井壁煤岩固相侵入带与滤液侵入带的渗透率比值Kγ、固相侵入带深度Hs对渗流增量比的影响规律。研究结果表明,弹簧-液压式封隔器采用了无骨架式胶筒、径向滑块和强力弹簧设计,解决了密集分段径向射流工具在筛管内的高频次封隔稳定性难题,实现了煤层气水平井筛管完井与射流增透一趟钻;在Hs=3.5 cm、Kγ=0.01条件下,筛孔径向水力射流间距减小为筛孔间距0.05 m,水平井段煤岩渗流增量比增加5.5%,实现了煤层水平井段密封分段径向射流增透作业。研究结果为解决采用筛管完井的煤层气水平井储层伤害难题提供技术指导,为近井壁煤岩增透作业提供理论支撑。

The permeability of coal near shaft wall is low for the reservoir damage,and the space of conventional segmented hydraulic jetting is long.A method of dense segmented radial jet with pre-drilled holes as nozzles was proposed to improve the permeability of coal near shaft wall,and the spring-hydraulic packer and liquid injection nipple were designed and optimized for horizontal well completion with pre-drilled liner.The calculation model of single pre-drilled hole radial jetting and seepage increment ratio of coal breaking cave near shaft wall are established.The number of pre-drilled holes per meter,exit jetting velocity of pre-drilled hole and flow rate were optimized.The influence of permeability ratio Kγbetween the solid intrusive zone and the filtrate intrusive zone and the depth of solid intrusion zone Hs on the seepage increment ratio of coal near the shaft wall is analyzed.The results show that the spring-hydraulic packer with a design of non-skeleton rubber cylinders,radial sliders,and strong tensile spring,which improves the stability of high-frequency sealing of the dense segmented radial jetting tools within the pre-drilled liner,achieving completion and reservoir stimulation in one trip for coalbed methane horizontal well.Under the conditions of Hs=3.5 cm and Kγ=0.01,the radial hydraulic jetting space of the pre-drilled liner was reduced to the pre-drilled hole space of 0.05 m,and the seepage increment ratio of coal methane horizontal well increased by 5.5%with dense segmented radial jetting.The research results provide technical guidance for solving the reservoir damage challenge in coalbed methane horizontal wells completed with pre-drilled liner,and theoretical basis for permeability enhancement operations in coal near shaft wall.