沁水盆地基于储层保护的煤层气水平井钻井液的研究

Research on coalbed methane drilling fluid for horizontal well based on coal reservoir protection in Qinshui Basin

清水作为煤层气水平井钻井液存在以下不足:与地层水相比,矿化度偏低存在水敏性损害;与地层水配伍性差,有结垢现象;不能有效絮凝细小煤屑颗粒,造成固相污染储层;返排能力不足。针对清水钻井液的不足,通过引入无机盐、防垢剂、表面活性剂和低分子量絮凝剂对清水钻井液进行改进。在此基础上,优选出煤层气水平井钻井液配方:清水+0.5%防膨絮凝剂PXA+0.5%防垢助排剂GPA。性能测试结果表明,改进后清水钻井液与煤层水、黏土矿物具有很好的配伍性,返排和絮凝能力增强,具有优异的储层保护效果。

Clear water for drilling fluid in CBM well has several defects,which includes water sensitivity for salinity difference,scaling damage between clear water and formation water,micro-particle invasion because of bad flocculation,and weak flow back ability.Clear water was modified for CBM horizontal well drilling fluid by addition of inorganic salt,surfactant,scale inhibitor and flocculant.Drilling fluid formulation optimized for CBM horizontal well is clear water＋0.5%PXA＋0.5%GPA,PXA and GPA are all reservoir protection agents.The performance test results show that this new drilling fluid has good compatibility between drilling fluid and formation water,good anti-swelling ability,strong flocculation ability and flow back easily.Clear water modified has excellent reservoir protection effect from damage.