摘要：In the drilling process,wellbore instability is a world-class problem in China and abroad.Strengthening the plugging effect of pores and fractures on the scale of nanometer and micrometer in shale formation and inhibiting the hydration of shale formation are the key measures to keep shale stability.A paraffin nano emulsion SLRY for drilling fluids was developed by using liquid paraffin as oil phase,Tween80 and Span80 as surfactants,n-butanol as cosurfactant and cationic surfactant CTAB as an electrical regulator.The particle size distribution of the emulsion system was narrow and the granularity was kept below 200 nm.The plugging performance of SLRY was evaluated by pressure penetration test.The hydration inhibition of SLRY was evaluated by shale swelling,dispersion and wettability tests.The results showed that the paraffin nanoemulsion SLRY could plug the pores and cracks of shale and reduce the permeability of shale.Positively charged emulsion droplets could adsorb on the clay surface and form hydrophobic film,which further reduced the contact between water molecules and clay,and effectively inhibited the hydration expansion and dispersion of shale.In addition,the compatibility of paraffin nano emulsion SLRY and water-based drilling fluids was better,which could improve the plugging and filtration loss performance of water-based drilling fluids.
