可降解甲酸盐钻井液的研究与应用

Research and application of decomposable formate base drilling fluid

大邑构造位于四川盆地龙门山冲断推覆构造带,主力气藏为须家河组二段,是一个低孔、低渗、常压、非均质极强、裂缝发育的致密砂岩储集层,并含有泥页岩夹层,储层保护工作难度大。针对常规钻井液固相多、抑制性差等特点,室内通过配方优化,研制出一套满足须二储层钻井施工及储层保护的甲酸盐无固相钻井液体系。经过性能评价,该体系具有优良的固相容纳能力和润滑能力,抗温达130℃,降解恢复率达94.49%。在DY6井、DY5井进行了现场应用,结果表明,可降解甲酸盐钻井液具有较好的气层保护性能,解决了井壁稳定问题,适合小井眼钻井,是适合大邑构造须家河组二段储层保护的一项新技术。

Dayi structure is located in Longmenshan thrust nappe zone of Sichuan basin.The second section of Xujiahe formation is the main formation,a sandstone gas reservoir,with the characteristics of low porosity,low permeability,normal pressure,high heterogeneity and fracture development.And it has mud shale intervals,which causes the difficulties of formation protection.According to the big amount of solid phase and low inhibitive ability of conventional drilling fluids,a formate clay-free drilling fluid system is developed,which meets the need of drilling operation and formation protection in the second section of Xujiahe formation.Through the performance evaluation,it is proved that the drilling system has high solid phase capacity and lubricating ability.The ability of its temperature stability reaches 130℃,and the damage recovery rate is 94.49%.It was firstly used inWell DY6 and DY5 in Dayi structure.And the results indicate that the decomposable formate base drilling fluid has high gas formation protection capacity,and solves the issue of wellbore stability.Besides,the drilling fluid is suitable for slim hole drilling.In general,the formate base drilling fluid is a novel technique for formation protection in the second section of Xujiahe formation of Dayi structure.