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

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 Δ G 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.