Effect of Lubricating Oil Composition on Damage and Fouling of Sandstone Reservoirs in Natural Gas Production
摘要
During natural gas drilling and production, the use of lubricating oil causes damage and fouling to sandstone reservoirs, thereby hindering the migration, diffusion, and extraction of oil and gas. In addition, reservoir fouling caused by lubricating oil and natural gas can also cause drilling and production machinery to get stuck and other related obstacles, and petroleum workers are actively exploring the causes of sandstone reservoir damage and related solutions to alleviate reservoir damage. This study is based on the geological characteristics of sandstone reservoirs, and establishes adsorption and diffusion models for natural gas and lubricating oil molecules according to the natural gas occurrence law. At the same time, the influence of lubricating oil composition and reservoir conditions on sandstone reservoir damage is analyzed. In addition, the micro mechanism of sandstone reservoir damage was revealed based on molecular dynamics and adsorption theory. The research results indicate that natural gas and lubricating oil components have both adsorption and desorption effects on the surface of sandstone, and Langmuir monolayer adsorption is the main cause of sandstone reservoir damage. Raising the reservoir temperature will reduce the adsorption capacity of methane and lubricating oil molecules, and the adsorption capacity of the reservoir will decrease from 0.53 mg/m3 at 40°C to 0.39 mg/m3 at 80°C. The increase in reservoir pressure exhibits a higher reservoir damage rate and lower permeability, which may be due to the enhanced adsorption of microscopic molecules on the sandstone surface caused by reservoir pressure. In addition, the increase in the molecular chain and content of lubricating oil can also reduce the reservoir damage rate from 9% to 20%, which may be due to the increase in the molecular chain of lubricating oil promoting the adsorption of molecules on the surface of sandstone. By analyzing the impact of lubricant composition and reservoir conditions on sandstone reservoir damage, convenient conditions and theoretical support can be provided for natural gas and reservoir development in sandstone reservoirs.