VTK垂直钻井技术在川东地区的应用

Application of the VertiTrak nonrotary drilling system in the eastern Sichuan Basin

四川盆地川东高陡构造区内的侏罗系沙溪庙组—下三叠统嘉陵江组地层岩性组合复杂、软硬交替频繁,属于典型的易井斜地层,采用常规的防斜技术虽能防斜,但因钻井参数受限,严重影响了机械钻速的提高。VertiTrak是贝克休斯公司最先进的垂直钻井系统,它是综合了闭环旋转导向系统、高性能X-TREME马达、可靠的随钻测试等3种技术而开发出来的一种闭环自动垂直钻井系统（简称VTK垂直钻井技术）。在川东地区试验应用了VTK垂直钻井技术,同时强化钻井参数、优化钻井液防塌及流变性能。结果表明,试验获得了成功：①在已经发生井斜的井段用VTK工具进行正常钻压钻进,较快地实现了井眼轨迹的平稳降斜;②纠斜任务完成后,正常钻压钻进过程中实现了稳斜防斜;③VTK垂直钻井防斜打快效果显著——钻压达25 t,机械钻速提高50%~60%,钻井周期缩短30%以上。该方法为实现川东高陡构造区沙溪庙组—嘉陵江组长段易斜地层的防斜打快探索出了一条新途径。

Well deviation easily occurs in such a challenging environment of high-steep structure in the eastern Sichuan Basin,where the Jurassic Shaximiao and upper Triassic Jialingjiang formations are characterized by the complexity and frequent alternation of hardness and softness.Although conventional well-deviation control technologies are available,the penetration rate(ROP) will be significantly reduced due to the limitation of drilling parameters.First,we introduce the Baker Hughes's VertiTrakTM nonrotary drilling system integrating the technologies of closed-loop rotary steering,high-performance X-TREME Coil over Top Drive drilling rigs,and reliable measurement while drilling(MWD).Then,we explain how this new technology was applied as a pilot test in the study area of the eastern Sichuan Basin.Finally,we draw the following conclusions from this successful experience.(1) A hole can be easily straightened by the VTK tools adopted in the already deviated well sections under normal weight on bit(WOB).(2) After inclination correction of a hole,the hole can be straightened under normal WOB.(3) As a result,under the WOB of 25 tons,the ROP can be improved by 50-60% and the drilling circle can be shortened by above 30%.This new technology provides a new means for well deviation and fast drilling in the highly dipping formations in this study area.