Experiment and Simulation of Nanoparticles from the Assembly of Poly(St-(1-Octene)-EGDMA) as a Nano-Plugging Agent in Water-Based Drilling Fluids

Nano-plugging agents have become the key to efficiently extracting shale gas, which is a clean energy source. Poly(St-(1-Octene)-EGDMA) was synthesized by emulsion polymerization of 1-octene, styrene (St), and ethylene dimethacrylate (EGDMA). Fourier transform infrared spectroscopy, laser scattering, thermogravimetric analysis, scanning electron microscopy (SEM), pressure transfer experiment, and artificial mud cake plugging experiments were used to characterize poly(St-(1-Octene)-EGDMA). The results indicate that poly(St-(1-Octene)-EGDMA) has a particle size of 38.8 nm. After 16 h at 180 °C, the particle size is 49 nm. Based on thermogravimetric analysis, poly(St-(1-Octene)-EGDMA) can tolerate temperatures up to 394 °C, demonstrating excellent high-temperature stability. The rheology of the drilling fluid remains unaltered by poly(St-(1-octene)-EGDMA). With the addition of 2% poly(St-(1-octene)-EGDMA) water-based drilling fluid, the permeability decreased to 2.4 × 10–3 mD and the blocking rate increased to 50%. Simulations are performed with Ansys Fluent 19.2 to verify the experimental results. The potential plugging mechanism of poly(St-(1-Octene)-EGDMA) as a plugging agent was explored. Shale nanopores and nanofractures are invaded by poly(St-(1-Octene)-EGDMA) under pressure. Shale nanopores and nanofractures are plugged by poly(St-(1-Octene)-EGDMA). In water-based drilling fluids, poly(St-(1-Octene)-EGDMA) has a broad range of applications as a possible nano-plugging agent.