高温裂隙花岗岩体ScCO2压裂原位渗流–传热特性试验研究

doi:10.3724/1000-6915.jrme.2024.0869

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Abstract Hot dry rock (HDR) geothermal reservoirs contain abundant natural fractures. Utilizing supercritical carbon dioxide (ScCO2) fracturing can activate and connect these fractures to form a complex fracture network, providing an effective method to enhance reservoir permeability and heat exchange. In-situ high-temperature fracturing experiments on fractured granite using ScCO2 are conducted at temperatures ranging from 100 ℃ to 300 ℃. The injection pressure curves, post-fracturing fracture network morphology, fracture surface characteristics, permeability and convective heat transfer coefficients for both ScCO2 and water fracturing under high-temperature conditions are analyzed. The results indicate that: (1) Compared to water fracturing, ScCO2 fracturing exhibits a slower pressure increase and a lower fracture initiation pressure. ScCO2 fracturing results in more spalling on the fracture surfaces, rendering them rougher. Additionally, ScCO2 fracturing of granite generates multiple branch fractures that connect more effectively with natural fractures. (2) The transient phase change of the fracturing fluid and the convective heat transfer of the fluid due to crack propagation lead to a decrease in fluid temperature at the fracturing zones as the fractures propagate. Notably, the greater the initial temperature of the granite, the more significant the decrease in fluid temperature. (3) The permeability of granite following ScCO2 fracturing is 4.38 to 5.18 times greater than that of water fracturing, with a non-steady seepage phenomenon occurring as the pressure gradient increases, further amplifying the difference in permeability between the two fracturing methods. For both ScCO2- and water-fractured granite, both outlet flow rate and permeability decrease with increasing temperature, with ScCO2 fracturing exhibiting a more pronounced reduction. Specifically, as the temperature rises from 100 ℃ to 300 ℃, the outlet flow rate and permeability of ScCO2-fractured granite decrease by 59.5% and 85.3%, respectively. (5) Although the produced fluid temperature increases with rising granite temperature, the convective heat transfer coefficient decreases due to reduced permeability under higher confining stress. Nevertheless, ScCO2-fractured granite maintains a convective heat transfer coefficient that is 8.68 to 9.68 times greater than that of water fracturing, demonstrating superior thermal exchange performance. This study provides theoretical guidance for fracturing stimulation and efficient geothermal energy extraction in hot dry rock reservoirs

Key words： rock mechanics ScCO2 fracturing high-temperature granite fracturing-permeability convective heat transfer characteristics geothermal exploitation

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	Articles by authors
	LI Zhiling1
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	CHEN Yuedu2
	LIANG Weiguo1
	2
	DU Wenjie2
	YAN Juncai1
	2

Cite this article:

LI Zhiling1,2,CHEN Yuedu2, et al. In-situ seepage and heat transfer characteristics of ScCO2 fracturing in high-temperature fractured granite[J]. , 2025, 44(8): 2086-2100.

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https://rockmech.whrsm.ac.cn/EN/10.3724/1000-6915.jrme.2024.0869 OR https://rockmech.whrsm.ac.cn/EN/Y2025/V44/I8/2086

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