Investigation Of CO₂-formation Brine-rock Reaction Of Shenhua Ordos CCS Project

Carbon dioxide capture and storage technology?CCS?,especially the geological storage of CO₂,is one of the most effective technologies to reduce CO₂ emissions.In order to study the safety of stratum and the stability of geological storage in the static sealing stage of Shenhua CCS demonstration project,in this paper,the cap rocks of the Zhifang formation and the reservoir rocks of the Liujiagou and the Majiagou formation from the Shenhua CCS demonstration project in Ordos are selected as the research target,CO₂-formation brine-rock reaction under in situ formation conditions was conducted to study the influence of CO₂ injected on the formation.Then the CMG-GEM software was used to simulate the long time geological sequestration reaction.Laboratory study showed that the concentration of HCO₃^-in the reaction liquid is obviously increased after CO₂ injection under the condition of high temperature and high pressure.The H⁺and CO₃^2-ions formed subsequently,then a series of geochemical reactions occurred.Some of reacted rock samples dissolved including the dissolution of quartz,feldspar minerals,clay minerals,etc,and the new minerals such as calcite,dolomite,dawsonite and chlorite were formed.The Ca²⁺+Mg²⁺concentration of the overall reaction fluid increased in a short time,which is beneficial to the whole process of geological storage.Meanwhile,the whole reaction had little influence on the pH value of the brine in the study area,which showed that the injection of CO₂ had little influence on the formation conditions of the study area.It was also illustrated that the safety of CO₂geological seal in this block is relatively high.The work also compared three selected rock samples from the dissolution rate,microstructure,the change of the pH value of the reaction fluid and the change of the ionic concentration of the reaction liquid.It can be concluded that the reservoir rocks of the Liujiagou formation is more suitable for the CO₂ geological sequestration reaction.,Based on reservoir rocks of the Liujiagou formation,CMG-GEM software was used to simulate the long-term CO₂ geological sequestration reaction.for a period of up to 500years.It was found that with the prolongation of the reaction time,the concentration of CO₂ and the concentration of Ca²⁺+Mg²⁺in the brine increase obviously,the rock dissolution rate increases and the mineralization rate of CO₂ increases gradually.The overall CO₂ storage capacity and seal effect are also ideal.Combining the laboratory study with the numerical simulation,it could provide further theoretical basis and scientific criterion for evaluating the adaptability and safety for the current phase?completed injecting?of Shenhua Ordos CCS demonstration project.