一种页岩气疏水强封堵水基钻井液

四川龙马溪组页岩地层水敏性强、微裂缝及裂缝发育，钻井过程中井壁坍塌事故频发，严重制约了页岩气的高效开发。为解决上述难题，引入了一种既能抑制页岩水化膨胀与分散，又能封堵孔隙、微裂缝及裂缝，同时使页岩表面疏水的改性二氧化硅封堵剂。并以该封堵剂为核心，优选降滤失剂、润滑剂等，研制了一种疏水强封堵水基钻井液。该钻井液既具有良好的流变性、降滤失性，又具有优异的抑制、封堵、疏水和抗污染能力。该钻井液的页岩回收率达90.2%，对40～60目砂床渗入深度仅为1.5 cm，密度为2.2 g/cm3时高温高压滤失量为7.2 mL。 

Research on A Water-based Drilling Fluid for Shale Gas Drainage and Strong Blocking

The shale formation of the Longmaxi Formation in Sichuan is highly water sensitive,with micro-cracks and cracks developed. During the drilling process, the shaft wall collapsed frequently,which severely restricted the efficient development of shale gas.In order to solve the above problems, this paper introduces a hydrophobically modified silica plugging agent that can not only inhibit shale hydration expansion and dispersion, but also block pores,micro-cracks and cracks, and make the shale surface hydrophobic.And with the core of the plugging agent, combined with fluid loss additives, lubricants, etc., a hydrophobic and strong plugging water-based drilling fluid was studied. The drilling fluid not only has good rheology and fluid loss reduction properties, but also has excellent inhibition, plugging,hydrophobic and anti-pollution capabilities. The shale recovery rate of the drilling fluid is 90.2%, the penetration depth into the 40-60 mesh sand bed is only 1.5 cm, and the high temperature and high pressure filtration loss is 7.2 mL when the density is 2.2 g/cm3.