基于Pickering乳液的油基钻井液

Pickering乳液通过颗粒在油水界面吸附，形成稳定界面膜防止水滴聚并，能够提高油基钻井液的稳定性。然而，关于Pickering乳液油基钻井液的研究，忽略了油相中水滴和无机亲水颗粒间相互作用，均未考虑配浆时加入的氢氧化钙、加重剂以及地层中进入的劣质固相等无机颗粒对乳液中水滴存在形式的影响。因此，向W/O型Pickering乳液中加入氢氧化钙、重晶石和不同水化程度高岭土颗粒，通过宏观沉降实验和显微镜图像证明水滴与颗粒结合，以结合水形式存在，导致颗粒聚集；通过激光共聚焦显微镜和低温差示扫描量热对结合水进行表征。通过添加分散剂可以促进结合水颗粒的分散，提高钻井液体系的稳定性。基于W/O型Pickering乳液的油基钻井液不是油包水乳液，而是结合水颗粒在油相中适度分散的体系。此外，配制低密度油基钻井液模型体系，并调控体系的流变性能，实现低温恒流变。

A Pickering Emulsion Oil Based Drilling Fluid

In a Pickering emulsion, the solid particle emulsifier is absorbed at the interface between oil and water, forming a stable interfacial film to prevent the coalescence of water droplets. This property can be used to improve the stability of oil based drilling fluids. However, in studies on the oil based drilling fluids based on Pickering emulsion, the interaction between a water droplet in the oil phase and an inorganic hydrophilic particle has been omitted; the effects of inorganic particles added to an oil based drilling fluid, such as calcium hydroxide, weighting agents and the drilled cuttings, on the existence of the water droplets in the emulsion are not considered. In laboratory study, calcium hydroxide, barite and kaolinite particles of different hydrating capacities were added into a W/O Pickering emulsion. Macro sedimentation experiment and microscope observation with microscopic images have proved that the water droplets are combined with the solid particles, existing in a form of bound water. This explains the aggregation of the solid particles. The bound water was characterized with laser confocal microscope and low temperature differential scanning calorimetry. The solid particles with bound water can be dispersed by treating the system with a dispersant, in this way the stability of the drilling fluid can be improved. An oil based drilling fluid based on W/O Pickering emulsion is not a water-in-oil (W/O) drilling fluid, it is, however, a system in which the bound water droplets are moderately dispersed into an oil phase. In addition, low temperature constant rheology can be achieved by adjusting the rheology of a low density oil based drilling fluid.