Seepage Characteristics Of Supercritical CO₂ In Sandstone And Influence Of Water-Rock Interaction

With the development of the economy,the amount of CO₂ in the atmosphere increases sharply because of the burning of fossil energy.The emission of greenhouse gases leads to global warming and has a serious impact on human's living environment and social and economic development.As the largest developing country in the world,China has long been the largest emitter of CO₂,and the task of emission reduction is urgent.CO₂ geological storage technology is considered as a direct and effective means of emission reduction,which injects captured CO₂ into underground reservoirs to reduce the CO₂ content in the air.Therefore,it has attracted extensive attention.CO₂ geological storage process,through the injector,supercritical CO₂ injected into the underground reservoir as acid gases,supercritical CO₂ have the characteristics of high density,low viscosity,in the process of the injection Wells near the CO2 flow rate is larger,as far away from the injection well,the flow velocity is reduced,at the same time will also with the reservoir rock water-rock effect,influence seepage process,for on the seepage properties of supercritical CO₂ in sandstone and water-rock effect to know there is insufficient,according to the above problem,In this paper,three sandstone samples with different permeability were selected to study the supercritical CO₂ percolation characteristics and co2-water-rock interaction under laboratory conditions.First of all,the quality of sandstone,material composition,mineral composition,surface structure,internal structure and porosity were tested,on this basis,the seepage experiment was carried out by supercritical CO₂,analyzes the characteristics of supercritical CO₂ seepage sandstone,and then carried out CO₂-water-rock interaction experiment,analyzes the water rock permeability and the influence of porosity of sandstone,on the basis of the effect on water rock after supercritical CO₂ seepage experiment in the sandstone again after CO₂-water-rock interaction is analyzed by seepage characteristics of sandstone,and supercritical CO₂ seepage model is established,and the results show that:?1?when the pressure gradient is small,supercritical CO₂ with convex curve between seepage velocity and pressure gradient,when the pressure gradient is larger,and the relationship between seepage velocity and pressure gradient in a straight line and the critical point between convex curve and straight line,after supercritical CO₂-water-rock interaction,the sandstone increases critical pressure gradient,the critical speed decreased;?2?in the process of CO₂-water-rock interaction,the permeability of sandstone in shanxi formation and taiyuan formation first increases and then flattens out with reaction time;the permeability of sandstone in chang 10 formation gradually decreases with reaction time and finally flattens out;?3?in the process of CO₂-water-rock interaction,since there are more calcium-containing minerals that can be dissolved in water,the concentration of calcium ions in the water sample is relatively high and remains at a high concentration.As the amount of dolomite in contact with water in sandstone decreases gradually,the concentration of magnesium ions in the solution decreases gradually;?4?according to the XRD test results,the three types of sandstone are mainly quartz and feldspar,containing a small amount of calcite,dolomite,clay and other minerals;?5?after CO₂-water-rock interaction,partial dissolution occurs on the inside of sandstone,and porosity increases.