Experimental Study on the Influence of Supercritical CO2 on Shale Fracture Morphology
In the ahead fracturing process of supercritical carbon dioxide （SC-CO2）， the injected CO2 is easy to enter the porous media of shale， and combined with the formation water or water-based fracturing fluid to form a slightly acidic fluid， thus stimulating the initiation and propagation of shale micro...
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| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | zho |
| Published: |
Editorial Office of China Petroleum Machinery
2025-06-01
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| Series: | Shiyou jixie |
| Subjects: | |
| Online Access: | http://www.syjxzz.com.cn/en/#/digest?ArticleID=4973 |
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| Summary: | In the ahead fracturing process of supercritical carbon dioxide （SC-CO2）， the injected CO2 is easy to enter the porous media of shale， and combined with the formation water or water-based fracturing fluid to form a slightly acidic fluid， thus stimulating the initiation and propagation of shale microfractures. To clarify the influence of CO2 on the initiation and propagation of shale microfractures， a combined experiment of pressurized soaking and uniaxial compression was carried out， and the influence of fluid type， soak time and soak sequence on the initiation and propagation of shale microfractures was studied. The study results show that the ahead injection of CO2 can promote the opening of bedding fractures， and the longer the CO2 action time， the more bedding fractures are opened. When the pressure drops， the bedding fractures opened by SC-CO2 are prone to close. However， when the “SC-CO2→water” composite action occurs， water easily enters the bedding fractures opened by CO2 to form effective support， reacts with CO2 to generate carbonic acid to dissolve carbonate minerals， weakens the mechanical strength of shale， promotes the propagation of microcracks， and forms a complex and stable fracture network. When the “water→SC-CO2” composite action occurs， water infiltrates into the small pores of shale under the action of pressure difference and capillary force， forming a large amount of water film on the pore wall， seriously hindering the diffusion of CO2 into the shale， and making it difficult to effectively open the bedding fractures. Moreover， the fracture propagation of vertical bedding samples is mainly controlled by loading stress， and the influence of fluid is weak. After cracking， a tilted fracture surface that penetrates the bedding is generally formed. The study results provide a theoretical basis for optimizing the technological parameter design of CO2 ahead fracturing of shale， and are of great significance for improving the development efficiency of shale oil and promoting the geological storage of CO2. |
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| ISSN: | 1001-4578 |