Impacts of injection temperature on the CO injection capacity in the different sloping formations.

The CO injection capacity directly affects the CO storage efficiency. Injection temperature and formation sloping degree affect the CO injection capacity. Based on the actual geological conditions of the Shiqianfeng Formation in the Ordos Basin of China, a three-dimensional (3D) simulation model was established to evaluate pressure, temperature, CO spatial distribution, and injection amount. A total of 17 simulation schemes were carried out using the TOUGH2-ECO2N fluid property module. The results showed that the injection temperature had a significant impact on the CO injection capacity in the different sloping degree formations. Increasing the injection temperature resulted in increased formation pressure, CO gas phase, dissolved phase, and total injection amount, while decreasing the CO concentration, and the formation pressure changed obviously with the formation sloping degree. The larger the formation sloping degree was, the less the CO injection amount. Higher injection temperature and smaller sloping degree formation were more favorable for CO injection, and the CO injection capacity was stronger, signaling that it should be selected to store CO in the future.