Estimation And Influencing Factors Analysis Of Dissolved CO₂ In Deep Saline Aquifers

Since the last two centuries,the growing carbon dioxide emissions of greenhouse gases in the atmosphere have received increasing attention.The increase of CO2 concentration is caused by anthropogenic emissions,most of which are related to the combustion of fossil fuels.The concentration of CO2 in the atmosphere is dynamic,and the concentration of CO2 in the 1950 s is about 315 ppm,and today’s concentration has increased to about 390 ppm.Carbon capture and storage(CCS)is one of the key technologies to reduce CO2 emissions,and one of the most important aspects is to store the captured CO2 safely in geological structure,especially in deep saline aquifers.In this paper,based on the deep study of CO2 storage mechanism in deep saline aquifers,the basic model was established to analyze the migration and distribution of CO2,and the influence of different influencing factors on the burial was analyzed.The mechanism of sequestration of carbon dioxide sequestration mainly includes structural trapping,residual gas trapping,solubility trapping,mineral trapping.The four kinds of sequestration mechanism of CO2 storage are not isolated,they work in the whole process of storage,but with the time scale changes,the proportion of various storage mechanisms are different.The migration of CO2 in the reservoir is mainly affected by the diffusion,convection and dissolution,and the three functions complement each other to promote the dissolution of CO2 in the brine.Temperature,pressure,porosity,permeability,groundwater salinity,injection rate and other factors will have an impact on CO2 storage.The solubility of CO2 decreased with the increase of temperature,and the dissolved amount of CO2 decreased,the increase of the temperature could not improve the flowability of CO2 to compensate for the decrease of the solubility;the solubility of CO2 increase with the increase of pressure,and the dissolved amount of CO2 increase,but the rate of increase is slow,which is due to the larger pressure lead to CO2 viscosity becomes larger,is not conducive to the flow of CO2;the dissolution of CO2 increased with the increase of porosity,and the increase of porosity could promote the CO2 flow,which has a positive influence on the CO2 storage;with the increase of permeability,there is an increasing trend of the dissolved amount of CO2,but the effect is little,the increase of permeability can make the CO2 distribution more uniform;the solubility of CO2 decreased with the increase of groundwater salinity,and the dissolved amount of CO2 decreased,because of the increase of salinity,the density difference between salt water and CO2 increased,which promoted the CO2 flow,the rate of decrease is slow;the change of injection rate has no effect on the dissolved stock,but in the initial stage of injection,if the velocity is too large,the flow of CO2 is fast,and the dissolution of CO2 tends to be stable after the injection is stopped.Multi-well injection of CO2 relative to single well injection has little effect on solubility trapping,and simultaneous mixing of water and CO2 is beneficial to increase dissolved and residual gas.