| CO2as an oil displacement agent for enhanced oil recovery method has become one of the important way of reservoir development. Especially for the low permeability tight reservoir, due to the porous medium of the reservoir has the large specific surface area, large adsorption capacity, small pore, large capillary pressure, low abundance and lightweight oil, which result in low permeability and production, and injection cannot be carried out or oil cannot be produced. The regular development way benefits poor or cannot effectively develop. Research and practice show that CO2injection is one of the effective ways to develop the low permeability tight reservoir at home and abroad.In recent years, the global climate continues to warm. The greenhouse gas emissions are paid more and more attention by people. Many countries have signed the Kyoto Protocol for the purpose of reducing greenhouse gas. China ranks second for the CO2emission. No matter from the responsibility of the international community, or from the viewpoint of sustainable development and creating a harmonious society in our country to set out, we are in urgent need to solve the problem of CO2emission reduction.The main way of CO2reduction is geological storage. CO2as an oil displacement agent is injected into the low permeability tight reservoir, which can not only solve difficult problems, but also can achieve long-term sequestration of COt at the same time. This process has the very broad application prospect. CO2has rich gas source, and it is easily miscible whit oil. CO2injection has high oil displacement efficiency. When CO2is in contact with crude oil under the reservoir condition, the non-equilibrium diffusion has important theoretical and practical significance to determine the shut-in time, match the air injection rate and the diffusion rate, describe transition zone of oil and gas and the miscible condition. The research on the non-equilibrium diffusion of CO2and oil in porous media is necessary.Non-equilibrium diffusion in porous medium is investigated through the theoretical and experimental methods. Also, this study is granted by the National Natural Science Foundation of China(theory research on non-equilibrium diffusion of CO2-multicomponent crude oil in porous media).Based on numerous literature researches at home and aboard, Non-equilibrium diffusion in porous medium is investigated through the theoretical and experimental methods. On the basis of study of the international and domestic molecular diffusion, firstly, establish the experimental test method of molecular diffusion between multi-components gases and actual crude oil in the PVT cell, and conduct four groups of testing experiments under different experimental conditions. Secondly, create the experimental test method and diffusion theory model of molecular diffusion between multi-component gases and actual crude oil in porous media, and the corresponding theoretical calculation method. The two sets of experimental testing are carried out under different temperature conditions.The main results achieved in this article are as follows:(1) Establish the experimental test method of molecular diffusion between multi-component gases and actual crude oil in porous media, and test the relationship between pressure and time in the diffusion process, oil-gas composition at final equilibrium state as well as the equilibrium time.(2) Establish the diffusion theory model and corresponding theoretical calculation method of molecular diffusion between multi-component gases and actual crude oil in porous media, consider1the fractal capillary pressure in this mode.(3) Calculate the molecular diffusion coefficient of CO2-oil system under high temperature and pressure in porous media, and analyze the influence of the system temperature and component of the crude oil on the molecular diffusion coefficient.(4) Compare the diffusion coefficient test of CO2-oil in PVT cell and in porous medium. And discuss the influence of porous medium on diffusion visually. Study indicated that porous medium hindered the molecular diffusion at some degree. And at the same temperature and pressure condition, diffusion coefficient of components of the same system at porous medium is smaller than that in PVT cell.(5) Analyze the influence of porosity and permeability on the molecular diffusion coefficient in porous media. |
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