Abstract: The properties of drilling fluid for drilling horizontal side-tracked slim hole were analyzed.In order to meet the requirements,the polymer coater,filtrate reducer,thinner,shale-control agent for drilling fluid were optimally selected,and an organic positive gel-polymer drilling fluid was developed.The properties of the new drilling fluid system,such as inhibition,mud cake-forming capacity,filtrate control capacity,rheology,lubricity and formation protection ability were tested in laboratory.The functional mechanism of the drilling fluid was briefly investigated.The field test was made at CPS 185 Well.In the whole drilling,the wall of the hole was stable,and the hole diameter was regular.Electric logging,running casing and cementing operation were successful.Laboratory tests and in-situ application indicate that this kind of drilling fluid has the advantages of both positive gel and polymer drilling fluids,such as unique rheology,and excellent lubricity,inhibition,anti-sloughing,formation protection property and easiness for field maintenance and treatment.The successful application at CPS 185 Well demonstrates that the organic positive gel-polymer drilling fluid can meet the requirements for drilling horizontal side-tracked slim hole.

Key words: horizontal hole, side-tracked slim hole, organic positive gel-polymer drilling fluid, borehole stability, formation protection

摘要： 分析了小井眼侧钻水平井对钻井液的要求.以新研制的有机正电胶为主剂,对聚合物包被剂、防塌剂、降滤失剂进行了优选实验,在此基础上研制了有机正电胶聚合物钻井液完井液.对该钻井液体系的抑制性、泥饼形成能力和控制滤失性能、流变性和润滑性以及对油气层的保护性能进行了评价实验,研究了该钻井液体系的作用机理.在侧平苏185井对该体系进行的现场试验表明,在整个钻进过程中,井壁稳定,井径规则,全井起、下钻畅通无阻,井下安全,电测井、下套管、固井作业顺利.室内实验和现场应用均表明,该钻井液兼有常规正电胶钻井液和聚合物钻井液的优点:具有独特的流变性及优良的润滑性;能抑制岩屑分散,能起到稳定井壁的作用;具有显著的保护油气层的特性,能够满足小井眼侧钻水平井的需要.

关键词: 水平井, 侧钻小井眼, 有机正电胶聚合物钻井液, 井眼稳定性, 油气层保护