鄂西水井沱组页岩水平井水基钻井液的实验研究

鄂宜页1井在寒武系水井沱组获得了高产页岩气流，但缺乏与之配套的高性能水基钻井液体系。对采自湖北省秭归县的水井沱组页岩露头，开展了X射线衍射和扫描电镜分析；进行了造浆黏土、盐类、纳米材料、降滤失剂、正电胶和表面活性剂等的遴选，基于电性抑制和润湿性控制方法，研发了一套SWDF高性能水基钻井液体系；对钻井液的流变性、滤失性、润滑性、抗温能力、抑制性和抗污染性能进行了综合评价。结果发现：①水井沱组页岩以石英、长石、方解石等脆性矿物为主，含量在55%～67%；黏土矿物以伊利石为主，含量在13%～27%，无蒙脱石，属弱膨胀性地层；②页岩表面的孔隙、微裂隙发育，为钻井液的侵入提供了天然通道；③ SWDF钻井液体系黏度与切力适中，API滤失量仅为7.2 mL，摩阻系数为0.21，可抗120℃高温，对页岩水化有较好的抑制性，有良好的抗盐、抗钙、抗黏土（模拟钻屑）侵能力，能满足鄂西地区水井沱组页岩水平井钻进需求。

Experimental Study on Water-based Drilling Fluid for Horizontal Drilling of the Shuijingtuo Shale Formation in West Hubei

A high performance water base drilling fluid was required to drill the well EYIYE-1 from which a high flow rate of shale gas was obtained. This well penetrated the Shuijingtuo formation of the Cambrian system. A series of laboratory work has been conducted to formulate an appropriate drilling fluid for the designed shale gas drilling. An outcrop of the Shuijingtuo shale formation, obtained from Zigui County, Hubei Province, was analyzed with XRD and SEM methods. Mud additives, such as clay, salts, nanomaterials, filter loss reducer, MMH and surfactants were selected through experiments. A high performance water base drilling fluid, SWDF, was formulated based on electric inhibition and wettability control. The SWDF drilling fluid was evaluated for its rheology, filtration property, lubricity, high temperature stability, shale inhibitive capacity and contamination resistance. It was found that 1) the Shuijingtuo shale formation is mainly composed of quartz, feldspar, and calcite etc.; the total amount of these brittle minerals accounts for 55%-67% of the shale sample. Illite is the main component of the clay minerals, which accounts for 13%-27% of the total clay. The shale formation contains no montmorillonite, and is therefore a weak-swelling formation. 2) the shale formation is developed with pores and micro-fissures which provided channels to drilling fluid invasion. 3) the SWDF drilling fluid has appropriate viscosity and gel strength, API filter loss of only 7.2 mL and friction coefficient of 0.21. SWDF is resistant to high temperature of 120 ℃, and shows good inhibitive capacity to shale hydration and high resistance to salt, calcium and formation clay (drilled cuttings) contamination; it is therefore suitable for use in drilling the horizontal Shuijingtuo shale formation in west Hubei area.