Preparation and Mechanism Study of Ternary Resin-Nano Silica Copolymer Lost Circulation Additive for Oil-Based Drilling Fluid

Abstract Due to the development of shale bedding and micro-fractures, it is very easy to induce complex downhole accidents such as leakage during the drilling of horizontal Wells, and the leakage of oil-based drilling fluid is serious, resulting in great economic losses. Aiming at the problems of poor compatibility and insufficient temperature resistance between chemical plugging materials and oil-based drilling fluids. In this paper, butyl acrylate, octadecyl methacrylate and sodium p-styrene sulfonate were selected as the copolymer, dibenzoyl peroxide as the initiator, divinylbenzene as the crosslinking agent, nano-silica as the toughening agent, and water as the dispersed phase. A ternary resin-nano silica copolymer lost circulation additive was prepared by suspension polymerization. The results showed that the molecular structure test of the resin lost circulation additive indicated that the unsaturated groups were grafted and the interpenetrating three-dimensional mesh structure was formed, with oil-absorbing and swelling properties at high temperatures and good mating properties. Under the condition of 140 ℃, the sealing experiment was carried out on the sand plate with a pore size of 1 mm, and the pressure capacity was up to 10.6 MPa. The particles compact and seal the leaking strata by deformation compaction and filling action. Compared with conventional plugging materials, resin lost circulation additive has good thermal stability and self-adaptability, easy to enter the pore space, micro-fracture, oil-based drilling fluid loss is effectively reduced.