摘要
渤海X油田东二段储层岩性疏松,水侵严重,岩心胶结差,取心作业中易发生钻井液冲掉岩心、堵心、磨心等问题,从而影响收获率。针对此问题,以2口井为实例,对密闭取心低收获率的现象及原因进行了分析,并提出了技术改进措施。研究显示,5号井两次发生堵心的井段均为含油砂岩层间较薄的不均匀泥质夹层,当钻具由疏松砂岩突然钻遇不均匀夹层时,钻压和钻速会突然变化,影响岩心进筒,刮落的外端岩心和夹层中较硬岩心极易卡住并在衬筒下端堆积,造成堵心。4号井由于岩心过于疏松胶结太差,不能保持柱状相对上移进入取心筒,岩心在钻头处堆积,造成堵心;且上部钻具组合在大井眼中环空间隙太大,导致钻具组合的刚性不足,取心工具在井底无法稳定工作。对两口井均提出了钻具、转速等方面的技术改进措施,后续取心收获率均达到100%。
Reservoir in the second member of Dongying Formation in Bohai X Oilfield features in loose lithology,severe water invasion,and poor core cement,so the core is easily washed away,plugged,or worn by drilling fluid during coring operation. As a result,the harvest rate is affected. To solve this problem,we took two wells as an example,analyzed the phenomenon of low harvest rate of sealed coring and its cause,and proposed countermeasures. Study indicated that the intervals of Well No. 5 occurring core plugging twice were inhomogeneous interlayers that were thin among oil-bearing sandstone layers. When drilling tools encountered inhomogeneous interlayers,drilling pressure and drilling rate would change abruptly,affecting core into the tube. And the scraped external core and the harder core in interlayers easily got stuck and accumulated at bottom of liner,and thus resulted in core plugging. The loose core in Well No. 4 was difficult to prop the upper core up and accumulated at the drilling bit,leading to ＂core plugging＂. Moreover,the upper drilling assemblage had too large annular clearance,as a result,the drilling assemblage lacked of hardness. So coring tools could not work steadily at the bottom of the well. We put forward improvement actions for the two wells in terms of drilling tools and rotational speed,and the follow-up coring harvest rate reached 100%.
出处
《非常规油气》
2016年第3期92-95,共4页
Unconventional Oil & Gas
关键词
密闭取心
收获率
疏松砂岩
渤海油田
Sealed coring
harvest rate
loose reservoir
Bohai Oilfield
