绒囊钻井流体在金坛储气库硬脆性泥岩地层的应用

Application of Fuzzy-ball Drilling Fluid in Hard Brittle Shale Formation in Jintan Gas Storage

金坛盐穴储气库建井过程中钻遇三垛组、戴南组裂隙发育硬脆性泥岩发生坍塌扩径、起下钻遇阻卡等井下复杂情况。采用绒囊添加适量甲酸钠,开发出既能抑制黏土水化又能实现内封堵抑制自由水侵入地层的强抑制封堵型钻井流体。室内通过泥岩滚动回收率测定添加过甲酸钠的绒囊体系抑制性,岩心封堵试验测定其封堵性。三垛组泥岩经清水浸泡的平均滚动回收率为28.19%,聚合物钻井液平均滚动回收率为50.66%,而绒囊钻井液的平均滚动回收率达93.52%,表明该体系抑制性极强。钻井液封堵含裂缝岩心后驱替,注入端压力上升至18 MPa,表明封堵能力强。应用于金坛茅X井三垛组、戴南组裂隙发育泥岩井段,起下钻无阻卡,电测一次成功,井径扩大率仅为8.2%,而邻井井径扩大率达18%。结果表明,绒囊与甲酸盐组配的强抑制封堵型钻井流体具备强抑制性和强封堵性,解决了裂隙发育泥岩地层井壁失稳的问题,为解决同类型地层难题提供可选择的技术。

Wellbore collapse,well wall caving-in and stuck pipe issues are extremely serious when drilling through the hard-brittle mudstone formation in the salt cavern gas storage well in Jintan area.To address this issue,an appropriate amount of sodium formate was added to fuzzy ball drilling fluid to develop a strongly suppressed plugging drilling fluid,which is not only able to inhibit the hydration of clay,but also to block the water and thereby prevent free water from invading the formation.The inhibitive property of the new drilling fluid as well as that of sodium chloride drilling fluid and polymer drilling fluid was tested through the measurement of rolling recovery rate of mudstone,while its plugging property was determined through the core blocking experiments.The results show that the average rolling recovery rates of the cores from Sanduo formation for sodium chloride,polymer and fuzzy-ball drilling fluid are respectively 28.19%,50.66%and 93.52%,indicating the strong inhibition of fuzzy ball drilling fluid,whereas the injection pressure of the fractured core after plugged with fuzzy ball drilling fluid rises to 18 MPa,implying its powerful plugging capability.The drilling fluid was applied to the fractured mudstone section of Dainan formation and Sanduo formation in well Jintanmao X,and the field application showed that there was no hindrance when tripping and the electrical logging operation succeeded all in one go.Most importantly,the diameter enlargement rate of the well was only 8.2%,while the that of the adjacent well is up to 18%.In conclusion,the fuzzy ball drilling fluid modified with strongly suppressed sodium formate has strong inhibition and excellent plugging capability,which can control the wellbore instability in the hard-brittle shale formation and provide alternative technology for solving similar problems in the unconventional formation.