新型水基钻井液在延长油田页岩气水平井的应用

页岩气钻井多采用油基钻井液,以解决井壁垮塌等复杂情况,但油基钻井液存在成本高和污染环境等弊端。随着新环保法公布和环保意识不断提升,研发出适合页岩气钻井的水基钻井液迫在眉睫。延长油田是国内首个国家级陆相页岩气示范区,为此,以延长油田为例,对延长油田延长组页岩矿物组成和微观结构进行了全面分析,揭示了该地区井壁失稳机理及钻井液构建思路。并在此基础上,对钻井液体系关键处理剂进行优选及配方实验,研发出了一套新型水基钻井液体系,其各项性能与油基钻井液相当,HTHP失水仅4.6mL,滚动回收率达到了95%以上,极压润滑系数0.103。现场应用结果表明,新型水基钻井液能够满足延长油田页岩气水平井对钻井液的性能要求,有效保证井下安全。同时,对国内页岩气水基钻井液的研究和发展具有一定的参考价值。

Application of new water-based drilling fluid in shale gas horizontal wells of Yanchang Oilfield

Oil based drilling fluid is often used in shale gas drilling to solve the complex situations such as wellbore collapse, but oil-based drilling fluid has many disadvantages such as high cost and environmental pollution. With the promulgation of new environmental protection law and increasing awareness of environmental protection, therefore, it is urgent to develop a water-based drilling fluid which is suitable for shale gas drilling. Yanchang Oilfield is the first national continental shale gas demonstration area in China, Therefore, taking it as an example, this paper analyzes comprehensively the mineral composition and microstructure of extended shale in Yanchang Oilfield, and reveals the mechanism of wellbore instability and the idea of drilling fluid construction in this area. On the basis of this, the key additives of drilling fluid system are optimized and the formula is tested. A new water-based drilling fluid system has been developed. The performance of it is equivalent to the oil-based drilling fluid. The loss of water at high temperature and pressure is only 4.6 mL, the rolling recovery is over 95%, and the lubrication coefficient of extreme pressure is 0.103. The field application results show that new water-based drilling fluid can meet the performance requirements of drilling fluid for the extended shale gas horizontal well and guarantee effectively the safety of downhole. At the same time, it has certain reference value for the research and development of the shale gas water-based drilling fluid in China.