Thermal modeling of CO2 in the injection well and reservoir at the Ordos CCS demonstration project, China

Carbon dioxide capture and storage is a new technology that can realize low-carbon utilization of fossil fuels in a large scale. The China Shenhua Group has built a 100,000 tons/year integrated CCS demonstration project in Ordos, China. This paper chose Ordos basin as the simulation site and developed a full-field model of a coupled injection well and reservoir to simulate the CO2 behavior during CO2 injection through the wellbore and reservoir, taking into account thermal exchanges with rocks and natural convection of water in the annulus. Information for CO2 temperature and pressure distributions in the wellbore and the reservoir, and their variation with time, were obtained. The simulation results for the temperature and pressure profiles of CO2 in the wellbore were consistent with the well data log within 8.5%. The three factors leading to CO2 temperature increase from the wellhead to bottomhole, heat extraction from rocks, compressibility and potential energy loss were analyzed both qualitatively and quantitatively. Comparison between the bottomhole temperature in our full-field model and the simplified model with a heat flux to substitute for the rock was conducted. Finally, the wellbore transient shut-in effect was simulated to predict the potential pressure drop and cooling at the wellhead.