Injection Of CO 2 Improves Gas Recovery And Storage Research

Currently, the greenhouse gas CO2 were injected into depleted gas reservoirs sequestration and enhanced oil recovery is one of the hotspots of the world research. Since the integrity and trap gas cap gas reservoir geological structure has been fully validated in the development phase of the long-term natural gas, CO2 increase gas recovery supporting carbon sequestration obtained abroad favor. And China has carried out in Jilin Oilfield reservoir CO2 injection field experiments and achieved good economic and social benefits, but studies CO2 injection gas reservoirs less. In China, there is a lot of waste at the edge of the gas reservoir or inefficient gas reservoirs, and gas reservoirs as potential underground CO2 sequestration have an objective range of sequestration potential.Through physical simulation experiments and numerical simulation methods to study the implementation of CO2 injected into depleted gas reservoirs to improve oil recovery and sequestration influence of different factors on the process of purging efficiency and CO2 sequestration efficiency, as well as different storage mechanisms'capacity. The main research results and knowledge of the paper are as follows:(1) Indoor long core displacement experiment results show that:the smaller the rate of displacement, CO2 breakthrough sooner, CH4 ultimate recovery is smaller; lower permeability core, when injected the same PV CO2 breakthrough earlier and the final CH4 recovery the lower; when high injection and low production time, gravity segregation can make CO2 breakthrough earlier, CH4 recovery lower; bound water can make CO2 breakthrough time delay, the final CH4 recovery and storage rates higher than dry core.(2) Diffusion coefficient experiment results show that:formation rock porosity and permeability properties of the better, the larger the aperture, the more favorable CO2 diffusion in porous media; the higher the temperature, the molecular motion increases and CO2 diffusion accelerate; with the increase of the equilibrium pressure gas injection, CO2 diffusion coefficient exponentially decreasing; the use of gravity segregation can make the lower part of the vertical diffusion of CO2 reduced.(3) The Z-factor calculation of CO2 shows:CO2 factor of Z exhibit deviations from the ideal gas bending characteristics, to the right of the critical point of the supercritical region is formed, showing the nature of gases and liquids.(4) CO2 and CH4 density decreases with increasing temperature, as the pressure increases; for CO2, when the pressure is less than 7.3MPa CO2 critical pressure, effect of temperature on the viscosity is very small, negligible, but when the pressure exceeds 7.3MPa after, CO2 viscosity decreases with increasing temperature; for CH4, when the pressure is less than 15MPa, the viscosity increases with increasing temperature, the pressure is greater than 15MPa, the viscosity decreases with increasing temperature.(5) One-dimensional long core simulation showed:when the temperature is close to the critical temperature of CO2 at a pressure of about UMPa, CO2/CH4 ratio of density and viscosity is the maximum. Therefore, when the gas reservoir temperature and pressure close to the temperature and pressure, supercritical C02 displacement and sequestration efficiency will be higher; the larger the injected gas purity, when breakthrough, the greater CH4 recovery and the volume of CO2 sequestration formations, buried the higher survival rates; and higher impurity content, the stronger will increase the diffusion between the gas mixture, so that a slight increase in the transition zone.(6) Two-dimensional profile model simulations indicate that:with respect to the formation of positive rhythm and complex rhythm, rhythm anti-sectional formation production wells have the latest CO2 breakthrough time, the maximum cumulative CH4 recovery, sequestration late smallest average reservoir pressure rises, maximum CO2 sequestration potential.(7) Component model to simulate that injecting CO2 to enhance CH4 recovery and sequestration when bottom water gas reservoirs abandoned, simulation results show that: Increased 5.8% CH4 recovery; In sequestration of different mechanisms, CO2 supercritical sequestration accounted for the largest, accounting for 83.78%, followed by CO2 dissolution of sequestration, accounting for12.67%, the CO2 stock of bondage buried at least, accounting for 3.85% but the increase sequestration of time, part of supercritical CO2 sequestration convert to trapped sequestration.