Abstract
The purpose of this study is to reduce the risk of leakage of CO2 geological storage by injecting the dissolved CO2 solution instead of the supercritical CO2 injection. The reservoir simulation method is used in this study to evaluate the contributions of the different trapping mechanisms, and the safety index method is used to evaluate the risk of CO2 leakage. The function of the dissolved CO2 solution injection is performed by a case study of a deep saline aquifer. Two scenarios are designed in this study: the traditional supercritical CO2 injection and the dissolved CO2 solution injection. The contributions of different trapping mechanisms, plume migrations, and the risk of leakage are evaluated and compared. The simulation results show that the risk of leakage via a natural pathway can be decreased by the approach of injecting dissolved CO2 solution instead of supercritical CO2. The amount of the CO2 retained by the safe trapping mechanisms in the dissolved CO2 solution injection scenario is greater than that in the supercritical CO2 scenario. The process of CO2 mineralization in the dissolved CO2 solution injection scenario is also much faster than that in the supercritical CO2 scenario. Changing the injection fluid from supercritical CO2 to a dissolved CO2 solution can significantly increase the safety of the CO2 geological storage. The risk of CO2 leakage from a reservoir can be eliminated because the injected CO2 can be trapped totally by safe trapping mechanisms.
Highlights
Since the Industrial Revolution, the consumption of fossil fuels in transportation, industrial, electrical, and other sectors has resulted in a large increase in greenhouse gas emissions, thereby promoting environmental disasters, such as global warming
The safety index (SFI) was estimated by the dynamic number of moles of CO2 retained by the trapping mechanisms after CO2 had been injected into the target reservoir
The safety index was defined as [12]: SFI = (nCO2(res) + nCO2(aq) + nCO2(ion) + nCO2(min) )/nCO2(inj) where nCO2(res) is the number of moles of the CO2 retained by the residual gas mechanism as immobile supercritical phase; nCO2(aq) is the number of moles of the CO2 retained by the solubility trapping mechanism; nCO2(ion) is the moles of the CO2 retained by the ionic trapping mechanism; nCO2(min) is the number of moles of the CO2 retained by the mineral trapping mechanism, and nCO2(inj) is the number of moles of injected CO2
Summary
Since the Industrial Revolution, the consumption of fossil fuels in transportation, industrial, electrical, and other sectors has resulted in a large increase in greenhouse gas emissions, thereby promoting environmental disasters, such as global warming. To promote environmental protection and to halt the consequences of climate change, remediation techniques are required to reduce anthropogenic CO2 emissions to keep the rise in global temperatures below 2 ◦ C above pre-industrial temperatures in the 21st century. Carbon capture and storage (CCS) is one of the solutions. CCS is a practical approach to cut down CO2 emissions by means of a series of technologies, including the capture, transportation, and storage of CO2. The most important issue for the CO2 geological storage is the risk of leakage. The risk of leakage can be reduced by a safe injection strategy with understanding the functions of different trapping mechanisms
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