Research on the Law and Influencing Factors of CO2 Reinjection and Storage in Saline Aquifer

As a potential carbon emission reduction technology, CO2 geological storage in saline aquifer is an effective means to achieve the goal of carbon neutrality. Because of the complex geological structure in saline aquifer, it is urgent to carry out research on the law and influencing factors of CO2 storage, so as to provide theoretical support for carbon storage. In this paper, a numerical simulation model of CO2 reinjection and storage was established by adopting numerical simulation and considering the kinetic characteristics of CO2-brine-rock reaction. The distribution law of CO2 in the formation and the variation of storage volume under different storage mechanisms were analyzed. The effects of injection rate and injection well location on CO2 storage were studied. The results show that the CO2 in the injected formation is distributed near the injection well and mainly migrates to the upper part of the injection well. In the process of storage, four storage mechanisms play a role at the same time. With the increase of time, the main storage modes of CO2 change from geological structural storage to residual gas storage and solubility storage. And mineral storage plays the main role after the storage time reaches thousands of years. With the increase of injection speed and the lower injection well location, the dimensionless sweep range of CO2 becomes larger and the distribution near the injection well becomes more uniform. These changes lead to the decrease of CO2 density, the increase of solubility in water, and the continuous improvement of CO2 storage. The concept of dimensionless sweep range is proposed, which can quantitatively consider the influence degree of different conditions on the storage. So as to provide preliminary exploration for the subsequent development technology in the field, and to ensure the successful implementation of the storage project.