乐山—龙女寺古隆起震旦系超深井快速钻井技术

Fast drilling technology of ultra deep wells in the Sinian reservoirs in the Leshan-Longnüsi palaeohigh,Sichuan Basin

四川盆地乐山—龙女寺古隆起震旦系埋藏深度在5 000～6 000m,地层可钻性差、纵向上多产层多压力系统等复杂地质条件制约了钻井速度。针对钻井提速难点,重点从井身结构、钻头个性化设计及有机盐钻井液体系等方面进行了攻关研究与现场试验,初步形成了适应该地区的钻井提速技术模式:①优化井身结构,较传统井身结构缩短了大尺寸井眼长度,减少了作业时间,同时又能够满足完井与后期生产作业的要求。②个性化设计PDC钻头,应用效果表明较已完钻井机械钻速提高了31%～473%,在侏罗系沙溪庙组试验刚体PDC钻头平均机械钻速16.57m/h,已接近空气钻进效果;在适合井段试验等壁厚长寿命螺杆配合PDC钻头复合钻进,机械钻速较常规转盘钻机械钻速提高44%。③配合使用有机盐低固相钻井液,抑制性较聚磺钻井液更强,亚微米粒子含量减少,实现了辅助提高机械钻速的效果,井壁较使用聚磺钻井液的更稳定。2012年完钻的6口深井平均机械钻速由1.69m/h提高到2.54m/h,平均钻井周期从302d缩短到189d,实现了该区震旦系超深井的安全快速钻井。

The Sinian strata of Leshan- Longntisi palaeohigh in the Sichuan Basin are of 5,000 - 6,000 m depth underground, where the drilling rate has been restricted by poor drillability of formations, multiple pay zones ＆ multiple pressure systems, and other complex geological conditions. In view of this, scientific research and field trials were performed, focusing on the welibore structure, specific design of a drill bit, and the innovative organic salt drilling fluid system, thus a fast drilling technology model was formed ap- plicable to this region, a. The wellbore structure is optimized; compared with the conventional one, the length of the large size bore- hole is shortened and the operating time is reduced; additionally, the requirements for well completion and later-stage production are fulfilled, b. The PDC bit is particularly designed to increase the penetration rate （ROP） by 31 - 473% ; with the rigid PDC bit, the average ROP in the Shaximiao Fm is up to 16.57 m/h, close to the effect of air drilling; with the composite drilling of the PDC bit and the equal-wall thickness screw rod with a long service life in proper well sections, the ROP is increased by 44 % higher than that by the normal rotary drilling, c. With the use of organic salt and a low-solid content, the innovative fluid system has a much higher inhibitive capacity compared with the polysulfonate drilling fluid and the content of sub-micron particles is also decreased, thus the ROP is improved and the well wall is more stable than that when using the polysulfonate drilling fluid. With the above techniques, the average ROP of 6 deep wells drilled and completed in this study area in 2012 was increased from 1.69 to 2.54 m/h, and the aver- age drilling cycle was shortened from 302 to 189 days.