Experimental Study Of Carbon Dioxide Diffusion In Oil-saturated Porous Media

Under the pressure of the growing demand for energy and environmental protection, it is practical significant for the in-depth research on greenhouse gas emissions and energy efficient. CO2flooding can be used to enhance oil recovery, as well as make CO2permanently sealed with a good prospect. In the process of CO2gas injection flooding, COt dissolved in the crude oil is affected by the function of slowly molecular diffusion. Gas containing diffusion coefficient in the liquid in the porous rock under reservoir conditions will affect the rate of diffusion of the gas, oil and gas miscible conditions. CO2-EOR (enhanced oil recovery) projects and geological storage of CO2, the determination of the diffusion coefficient for the engineering design, risk assessment, economic evaluation and performance prediction is very necessary.Dual-chamber pressure decay method improvements, combined with MRI technology to develop a new method of diffusion coefficient, in addition to traditional experimental methods of diffusion coefficients calculated from the macroscopic diffusion coefficient function, at the micro level of flooding gas in The bulky state and porous media diffusion process intuitive visual, fast, real-time monitoring.Using the experimental system for the determination of the diffusion coefficient of the same temperature for different pressures of CO2and the bulk-decane, experimental results show that the diffusion coefficient in bulk decane, CO2, under with experimental pressure rises and increased with consistent with the trend in the literature at24℃, this is because when the pressure increases, the molecular kinetic energy increases, the viscosity of the liquid phase did not significantly improve. Each experiment the initial pressure and the equilibrium pressure difference between the close, indicating that the gas diffusion to the amount of liquid in the diffusion flux affected by the pressure, but with the nature of the gas-liquid itself.The traditional method of volume method for the determination of the porosity of sand filling model of porous media, combined with CT experiment random walk method and empirical formula method the sand filling model tortuous value, and compared. For isotropic porous media, sand filling model, the greater the sand particle size, the more close to the large volume, the smaller the degree of bending of the actual pore channels, the smaller tortuosity.In the obtained porous media based on the parameters, the diffusion coefficient of CO2in decane saturated porous media. Been measured at24℃under three kinds of sand in four different pressure points of the diffusion coefficient, the results show that the diffusion coefficient of CO2in decane decreases with the increase of tortuosity by shouted structure obvious impact.This paper established a dual-chamber pressure decay method combined with magnetic resonance imaging measurement flooding the diffusion coefficient of the effectiveness of the process, for in-depth analysis of the diffusion process of CO2in the large volume of oil and oil saturated porous media provides important experimental methods and analysis of ideas.