暂闭井带压作业机控压钻磨水泥塞技术及应用

The Technology of Drilling Cement Plug of Temporarilly-Closed Wells with Snubbing Unit and Its Application

修井机和连续管钻开暂闭井上部井段水泥塞后,水泥塞下方的圈闭压力突然释放易导致钻具飞出、设备和钻具受损以及井喷事故。采用带压作业机控压钻磨暂闭井上部井段水泥塞,能在管柱自重基础上施加足够高的下压力,工作防喷器回压控制能力高,钻塞管柱刚度强,能有效预防此类事件发生。针对带压作业机钻磨水泥塞存在的技术难点,从防喷器组合、地面流程、钻具组合、施工工艺等方面进行优化设计,形成一套“主动加压+复合旋转+平衡背压”的带压作业机控压钻磨水泥塞技术,能够有效应对桥塞或水泥塞下方可能圈闭有高压的风险,满足暂闭井钻塞的施工要求,且对道路、场地要求低,不需基建,作业周期短,可大幅降低作业成本。该技术在现场应用11井次,效果良好,为暂闭井、高压气井钻塞作业提供了技术借鉴。

After the workover rig or coiled tubing drilled the cement plug in the upper section of the temporarily closed well,the trapped-pressure below the cement plug may be suddenly released,which will lead to the flying out of drilling tools,damage to equipment and drilling tools and blowout accidents.Using snubbing operation technology to drill and mill the cement plug in the upper section of temporarily closed well can effectively prevent such accidents,for the snubbing unit can exert enough down-force based on the weight of the drilling column,be capable of handling higher back pressure with its working blow-out preventer and has tougher drilling column.In this paper,to solve technical difficulties of drilling cement plug with snubbing unit,a set of drilling and milling cement plug technology “positive pressuring+composite rotating+balancing back pressure” has been formed including BOP assembly,surface flow-back system,BHA and operation process,etc.This technology has effectively handled high pressure trapped under cement plug and satisfy operating requirements of plug milling of temporarily-closed wells and high pressure wells.Besides,it has such advantages as low requirements for transportation and operation space,no capital construction,short operation period and low operation cost.This technology has been successfully used for 11 jobs with good results,accumulating valuable experience for drilling cement plugs of temporarilly-closed or high pressure wells.