黔西地区表层易漏地层钻井工程技术

Drilling techniques for thief zones in surface formations in Western Guizhou

黔西地区是煤层气和页岩气重要的勘探区,碳酸盐岩发育,表层很容易钻遇溶洞、裂缝,发生井漏、井垮等复杂问题,给钻井工程带来很大挑战。根据黔西地区的地质情况和钻井工程实践,结合周边相似地区的钻井工程经验,分析表层碳酸盐岩地层井漏主要为溶洞性漏失和裂缝性漏失,并伴有井垮风险。对易漏易垮的复杂情况,提出了煤层气井和页岩气井针对性的井身结构设计,以降低井漏风险;并总结形成了空气钻进、清水钻进、空气潜孔锤跟管钻进、气体反循环钻进等应对黔西地区表层易漏、垮塌复杂情况的钻井工艺技术体系。最后,介绍了黔水地1井导管段复杂情况的处理经验。本文可为黔西地区表层易漏地层的优快钻井提供技术思路和借鉴。

Western Guizhou is an important area for exploration of both coalbed methane and shale gas,and presents huge challenge for drilling engineering because of circulation loss induced by karst caves and fractures.Analysis of the surface geological condition and drilling practice in the area with reference to the drilling experience from nearby areas finds that circulation loss,often accompanied by wellbore collapse,is mainly caused by the caves and fractures developed in Western Guizhou.In view of circulation loss and wellbore collapse,it is proposed that the specific well structure should be designed for the coalbed methane well and the shale gas well to prevent circulation loss and wellbore collapse.The drilling technical system,including air drilling,water drilling,casing while drilling,reverse circulation,has been developed to deal with the challenges and to increase the ROP.The drilling experience from Well QSD-1 is also described.This paper can provide the technological solution and reference for drilling in Western Guizhou.