Carbon dioxide (CO2) mineral trapping was considered the most secure and stable mechanism for CO2 geological storage. The previous studies lacked clarity regarding the mechanisms and processes of transformation for various types of minerals involved in CO2–water–sandstone and mudstone reactions during CO2 geological storage. Additionally, it didn't clear the different stages of mineral reactions in reservoir and caprock. We utilized experimental and numerical simulation methods to analyze the mechanisms, processes, and stages of CO2–water–rock reactions involving various types of minerals in the mudstone from Chang 4 + 5 members and the sandstone from Chang 6 member of the Triassic Yanchang Formation in the Ordos Basin. The experimental simulation demonstrated the dissolution of feldspar minerals in sandstone led to precipitate of carbonate, clay, and other minerals. Contrary, mudstone primarily underwent the dissolution of clay minerals and the precipitation of feldspar minerals, whereas carbonate content remained relatively stable. The numerical simulation consisted of experimental results in the short term, but over a longer timescale, The reaction processes of carbonate and clay minerals in the reservoir and caprock dissolved first and then precipitated. Conversely, other minerals behaved oppositely; feldspar minerals continuously dissolved in the reservoir but precipitated first and then dissolved in the caprock. The reaction stages of mineral change in both the reservoir and caprock could be divided into dissolution, rapid precipitation, and stable precipitation. The reservoir's dissolution stage was shorter than the caprock, which entered the stable precipitation stage earlier. With increasing storage time, continuous CO2–water–rock reactions gradually transformed physically sequestered CO2 in the formation into chemically sequestered mineralized CO2.