龙凤山气田强抑制封堵型防塌钻井液技术

龙凤山气田泉头组及以上地层水敏性泥页岩发育，在钻井过程中经常发生垮塌、卡钻、扩径和泥包钻头等复杂情况，营城组地层裂缝发育，易发生井漏。针对该地区的地质特征与钻井要求，通过水化膨胀实验和抑制膨润土造浆实验，优选胺钾复合抑制剂NK-1作为钻井液抑制剂；通过失水造壁性能评价实验和岩心渗透率测试实验，优选了降滤失剂KFT-Ⅱ和封堵防塌剂ZX-8作为钻井液封堵防塌剂，在此基础上研制了强抑制封堵型防塌钻井液体系，并对其性能进行了综合评价。实验结果表明，该钻井液具有良好的流变性、失水造壁性、抑制性和封堵防塌性。在北209井的现场应用中，钻井液性能稳定，封堵性和防塌性能突出，解决了全井的井壁失稳问题，起下钻、电测和下套管作业无遇阻，满足了现场钻井施工和储层保护的需要。 

Plugging Inhibitive Drilling Fluid Used in Longfengshan Gas Field

The Quantou Formation and the formations above in Longfengshan gas field are mainly water sensitive shales. Downhole troubles such as borehole wall collapse, pipe sticking, wellbone expansion and bit balling have frequently been encountered in drilling these formations. Lost circulation, on the other hand, has always been encountered in the Yingcheng Formation, which is full of fractures. To ensure safe drilling through these formations, a plugging inhibitive drilling fluid was formulated based on laboratory researches. A shale inhibitor, NK-1, was selected through shale core swelling test and bentonite hydration test. KFT-II and ZX-8, as plugging agent and anti-collapse agent, were selected through mud cake building test and core permeability experiment. Laboratory evaluation showed that this drilling fluid had stable rheology, good filtration characteristics, strong inhibitive capacity and plugging and anti-collapse performance. In field application, the well Bei-209 was drilled successfully with this drilling fluid. The drilling fluid had stable rheology, and no borehole wall collapse happened. Tripping of drill string, wireline logging and casing running were run with no hindrance, and the reservoir formations were fairly protected from being damaged.