Preparation and Performance Evaluation of Raspberry-Like Polymer Nano-Micro Plugging Agent

In order to solve the problem of wellbore instability in hard and brittle shale formations, nano-micro plugging agents have been developed in China and abroad by emulsion polymerization method. However, the nano-micro size of the plugging agent during application is difficult to maintain, and the drilling fluid is easy to foam. To this end, styrene and methyl methacrylate were used as monomers for polymerization, and divinylbenzene was used as an internal crosslinking agent for polymerization, with starch nanoparticles as emulsion stabilizers. A raspberry-like nano-micro plugging agent (i.e. raspberry-like crosslinked P (St-co-MMA) microspheres with starch nanoparticles adsorbed on the surface) was prepared by Pickering emulsion polymerization method for water-based drilling fluids. The particle size, morphology, and structure characteristics of crosslinked P(St-co-MMA) microspheres were characterized and analyzed, and their performance was evaluated in laboratory tests. The results show that the crosslinked P (St-co-MMA) microspheres can significantly reduce the American Petroleum Institute (API) filtrate loss and permeability plugging apparatus (PPA) filtrate loss of polymer potassium chloride drilling fluid and effectively plug the micron pores of the formation. The foaming problem of drilling fluid is solved, and the rheological property of drilling fluid is less affected, which can meet the needs of wellbore stability of shale oil and gas formation.