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

Abstract

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.