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Thermal cracking effect of liquid nitrogen on shale and its application analysis in hydraulic fracturing |
CAI Chengzheng1,2, LI Gensheng2, HUANG Zhongwei2, GAO Feng1
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(1.State Key Laboratory for GeoMechanics and Deep Underground Engineering, China University of Mining and Technology, Xuzhou 221116, China;2.State Key Laboratory of Petroleum Resources and Prospecting in China University of Petroleum, Beijing 102249, China)
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Abstract: |
In order to investigate the effect of liquid nitrogen on thermal cracking of shale rocks, ultrasonic and permeability tests were performed on the shale rock samples before and after being soaked in liquid nitrogen. The cracking mechanism of liquid nitrogen and its influencing factors were analyzed. The advantages and prospects for liquid nitrogen to be used as a fracturing fluid in shale gas development were discussed. The experimental results indicate that obvious thermal cracks can be observed on the surface of the shale samples after the soaking in liquid nitrogen. The rapid cooling effect of liquid nitrogen can promote the growth of micro cracks inside the shale samples, resulting in the reduction of sound velocity and increase in permeability. The reduction in sound velocity was up to 10.43% while the increase in permeability can be over 177.27%. |
Key words: shale gas liquid nitrogen cracking permeability application prospect |
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