煤层气超低密度固井技术研究与应用

摘要

针对煤储层低压、低渗、胶结性差等特点引发的固井难题,通过减轻剂、水泥体系基准配方、低温早强稳定剂、降失水剂和分散剂的实验优选,研发出中空玻璃微珠超低密度水泥浆体系,并研究设计了暂堵型前置液体系,形成了煤层气超低密度固井技术。优选的中空玻璃微珠减轻剂的表面不存在孔洞等毛细孔道,具备很好的耐压和抗剪切性能。超低密度水泥浆体系具有无游离液、浆体稳定、API失水量小（≤45 mL/30 min）、稠化时间可调、低温早强等优异性能。暂堵型前置液体系控制滤失能力强（≤19 mL/30 min）,能有效地封堵住3号煤层岩芯的裂缝和孔隙,与水泥浆相容性良好。应用研发的超低密度固井技术在沁南示范区成功进行了2口井的现场试验,固井水泥浆密度分别为1.15,1.20 g/cm3,固井质量合格率为100%,优质率达到96%以上。%There are many problems in coalbed methane cementing resulted from the characteristics of coalbed formation,such as low pressure,low permeability and weak cementation.Aimed to solve these problems,evaluation experiments of light weight additive,baseline formula of cement system,low temperature early strength stabilizer,fluid loss additive and dispersing agent were performed.On this basis,the ultra low density cement slurry was developed.Besides,bridging type preflush was researched.The ultra low density cement slurry and bridging type preflush formed the ultra low density cementing technology for coalbed methane.There is no capillary channel in the surface of preferred hollow glass microsphere,so it has good resistance to pressure and shear.The ultra low density cement slurry has many good performances,such as no free liquid,slurry stability,small API filtration loss(≤45 mL/30 min),adjustable thickening time and early strength at low temperature.Moreover,the bridging type preflush has good filtration control property(≤19 mL/30 min),effective shut off capacity to the fractures and pores in the No.3 coalbed core,and good compatibility with ultra low density cement slurry.This ultra low density cementing technology has been applied in two wells for field trial successfully at Qinnan demonstration plot,and the service density is respectively 1.15 g/cm3 and 1.20 g/cm3.Acceptability of cement job quality is 100%,and high quality is above 96%.