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标题：Geothermal energy exploitation from depleted high-temperature gas reservoirs by recycling CO 2: The superiority and existing problems
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作者：Guodong Cui ; Shaoran Ren ; Bin Dou 等
期刊名称：Geoscience Frontiers
印刷版ISSN：1674-9871
出版年度：2021
卷号：12
期号：6
页码：1-16
DOI：10.1016/j.gsf.2020.08.014
语种：English
出版社：Elsevier
摘要：AbstractCO2can be used as an alternative injectant to exploit geothermal energy from depleted high-temperature gas reservoirs due to its high mobility and unique thermal properties. However, there has been a lack of systematic analysis on the heat mining mechanism and performance of CO2, as well as the problems that may occur during geothermal energy exploitation at specific gas reservoir conditions. In this paper, a base numerical simulation model of a typical depleted high-temperature gas reservoir was established to simulate the geothermal energy exploitation processes via recycling CO2and water, with a view to investigate whether and/or at which conditions CO2is more suitable than water for geothermal energy exploitation. The problems that may occur during the CO2-based geothermal energy exploitation were also analyzed along with proposed feasible solutions. The results indicate that, for a depleted low-permeability gas reservoir with dimensions of 1000 m × 500 m × 50 m and temperature of 150 °C using a single injection-production well group for 40 years of operation, the heat mining rate of CO2can be up to 3.8 MW at a circulation flow rate of 18 kg s−1due to its high mobility along with the flow path in the gas reservoir, while the heat mining rate of water is only about 2 MW due to limitations on the injectivity and mobility. The reservoir physical property and injection-production scheme have some effects on the heat mining rate, but CO2always has better performance than water at most reservoir and operation conditions, even under a high water saturation. The main problems for CO2circulation are wellbore corrosion and salt precipitation that can occur when the reservoir has high water saturation and high salinity, in which serious salt precipitation can reduce formation permeability and result in a decline of CO2heat mining rate (e.g. up to 24% reduction). It is proposed to apply a low-salinity water slug before CO2injection to reduce the damage caused by salt precipitation. For high-permeability gas reservoirs with high water saturation and high salinity, the superiority of CO2as a heat transmission fluid becomes obscure and water injection is recommended.Graphical abstractDisplay OmittedHighlights•CO2has better heat mining performance due to its high mobility along with the flow•CO2injection during the stages of EGR and pressure build-up has little effect•CO2is suggested to exploit geothermal energy from almost all the gas reservoirs•Serious salt precipitation affects geothermal exploitation at high water saturation•The advantage of CO2becomes obscure at high permeability, water saturation, and salinity
关键词：KeywordsDepleted high-temperature gas reservoirHeat transmission fluidGeothermal energy exploitationCO2Salt precipitation