Experimental Study On The Mechanism Of Geological Storage Of Supercritical Carbon Dioxide

In the context of emissions of greenhouse gases and continued deteriorating of global cimate,carbon dioxide reduction has become an extremely urgent task.As an effective measure of reducing the contant of CO2 in our atmosphere, CCS (Carbon dioxide Capture and Storage) has been favored by many countries.CCS geological reservoirs for storage includes oil field/gas reservoir,abandoned coalbed reservoir and saline aquifer.According to the special report on Carbon dioxide Capture and Storage released by the Intergovernmental Panel on Climate Change,saline aquifer storage is the most potential methord of these three.The pressure and temperature in the target injection formation keep CO2 in a supercritical state.The characteristics of high densitylow viscosity and good mobility of supercritical CO2 benefits the injection and storage of CO2 in the saline aquifers.After injection of CO2 in the saline aquifer,buoyant force drives CO2 upward to the top of the cap rock within the formation,then affected by the static trapping,residual trapping,solubility trapping and mineral trapping,CO2 finally stored in the target formation.The storage of CO2 in saline aquifers involve complicated physical and chemical process,such as CO2 migration in the porous media,advecion and diffusion of CO2 in the saline,long term CC>2-saline-mineral contact causing geo-chemical reactions.This paper focus on the flow mechanism of supercritical CO2 under the pressure and temperature condition of formation,designs an apparatus that simulate the underground condition for CO2 to displace saline in the aquifer.Use the apparatus to lauche a series of experiment to measure the relative permeability curve of supercritical CO2 and saline under different conditions of permeability,temperature and pressure, figure out the law of varying relative permeability curves.By analyzing the result of the experiment,we can recognize that the lower the rock's permeability is,the lower of the Swj will be,and the relative permeability of CO2 and saline will be;when temperature rises,the relative permeability will fall,krg under the state of Swi will decline;the pressure of the experiment increases,the variation trend of the curve turns more rapidly, and the final relative permeability of CO2 under Swi turns out to be higher.Through xrd and fluid analysis, we juxtaposed the component change of the mineral composition in the sample before and after the CO2 displacement,noticed the chemical reacton mechanism in a relative short time injection process.We see that Quartz,Potash Feldspar and Plagioclase don't involve in the chemical change when CO2 displaced the saline in the experiment as their quality didn't change;but the quality of Calcite changed obviously,so we can know that Calcite is the main component of chemical trapping.