Synthesis and Plugging Performance of Poly (MMA-BA-ST) as a Plugging Agent in Oil-Based Drilling Fluid.

Nanopolymer was developed in order to solve the problem that the micron-scale plugging agent cannot effectively plug nanopores, which leads to instability of the wellbore. The oil-based nano plugging agent poly (MMA-BA-ST) was synthesized by Michael addition reaction using styrene, methyl methacrylate and butyl acrylate compounds as raw materials. Poly (MMA-BA-ST) has a particle size distribution of 43.98–248.80 nm, with an average particle size of 108.70 nm, and can resist high temperatures of up to 364 °C. Poly (MMA-BA-ST) has little effect on the rheological performance parameters of drilling fluids, no significant change in the emulsion breaking voltage, significant improvement in the yield point of drilling fluids and good stability of drilling fluids. The mud cake experiment, and artificial rock properties of poly (MMA-BA-ST), showed that the best-plugging effect was achieved at 0.5% addition, with a mud cake permeability of 6.3 × 10−5 mD, a plugging rate of 72.12%, an artificial core permeability of 4.1 × 10−4 mD and a plugging rate of 88.41%. The nano plugging agent poly (MMA-BA-ST) can enter the nanopore joints under the action of formation pressure to form an effective seal, thus reducing the effect of filtrate intrusion on well wall stability. [ABSTRACT FROM AUTHOR]