含绒囊结构的新型低密度钻井液

含绒囊结构的水基钻井液由定位剂、成层剂及成膜剂等处理剂配制而成。显微镜下观察发现，绒囊结构由内向外为气核、表面张力降低膜、高黏水层、高黏水层固定膜、水溶性改善膜、聚合物高分子和表面活性剂的浓度过渡层。室内配制了密度为0.85g/cm³ 的含绒囊结构钻井液。静态填砂堵漏实验和动静态岩心封堵实验表明，绒囊可根据地层渗流通道自行改变形态或改变性能，占据地层渗流通道或形成外黏膜层，封堵漏失通道。现场应用表明，含绒囊结构钻井液是一种新型的封堵低压漏失地层的钻井液体系。

Novel low-density drilling fluid containing fuzzy ball structure

The water-based drilling fluid containing fuzzy ball is made of PAC, HES, SDBS and other agents. The optical microscope images show that the fuzzy ball is composed of gas core, surface tension-reducing membrane, high-viscosity water layer, fixing membrane of high-viscosity water layer, compatibility-enhancing membrane, concentration transition layer of polymer macromolecule and surfactants from its center to outward. The solid-free fuzzy ball drilling fluid with the density of 0.85 g/cm³ was prepared in laboratory. The static sand-packing plugging experiments and the plus dynamic-static core-plugging experiments showed that the shapes and properties of the fuzzy balls in the drilling fluid could be changed depending on the flow channel dimension. The fuzzy balls of the drilling fluid could directly plug the flow paths or build-up outside mucous membrane to plug the circulation-lost channels. The field applications demonstrate that the novel fuzzy ball drilling fluid is suitable for plugging the low-pressure circulation-lost zones.