Application of Nano-Polymer Emulsion for Inhibiting Shale Self-Imbibition in Water-Based Drilling Fluids

摘要

In order to effectively solve shale instability problems in the drilling process, the remarkable capillary effect of shale formations cannot be ignored. In this paper, we report the development and characterization of a nano-polymer emulsion (SDPE) as a shale self-imbibition control agent in water-based drilling fluids. Spontaneous imbibition experiments, surface tension measurements, contact angle measurements, particle size distribution analysis, linear swelling tests, and hot-rolling cuttings dispersion tests were conducted to evaluate the comprehensive performance of SDPE. The results show that the water absorption of shale samples in SDPE emulsions is significantly less than in deionized water. At a concentration of 2.0%, the absorption mass decreased from 7.51 to 2.59%. Reducing the surface tension of the testing fluids, increasing the contact angle of the shale samples, and maintaining the nanoscale size were the important considerations for SDPE to greatly decrease the capillary effect. The low swelling rate and high recovery rate indicate that SDPE also exhibits strong shale hydration inhibition performance. Compared with water-based drilling fluids without SDPE, drilling fluids with SDPE present higher yield point/plastic viscosity values, and also decrease the filtration loss. Based on our findings, SDPE has the potential to be a good shale self-imbibition control agent and to help mitigate the shale instability problems.