Performance Evaluation of an Octadecyltrimethyl Ammonium Chloride–Dimethyl Silicone Oil as a Waterproof Locking Agent in Low-Permeability Reservoirs

[Image: see text] Low porosity and permeability of oil and gas reservoirs make it difficult to develop these resources. To address these problems, we developed and evaluated a novel, environmentally friendly waterproof locking agent, which was prepared using dimethyl silicone oil and octadecyltrimethylammonium chloride and characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and particle size measurement. The waterproof locking performance of the agent was evaluated in a low-permeability reservoir using surface tension and contact angle measurements, and thermodynamic calculations were performed. The average particle size or median diameter (D(50)) of a 1% mother liquor was 325 nm at 20 °C and 470.8 nm at 70 °C. The contact angle of clean water on the core surface increased from 10 to 110°. At 70 °C, the surface tension of water was reduced to 24 mN·m(–1), indicating good waterproof locking performance. The interaction parameters were calculated in accordance with the Langmuir adsorption theory. The increase in temperature from 20 to 70 °C reduced Γ(max) from 4.59 × 10(–6) to 1.36 × 10(–6) mol·m(–2) and ΔG(θ) from −40.93 to −56.54 kJ·mol(–1). Thus, the adsorption behavior of the developed locking agent is believed to improve the productivity of oil wells.