The Flow Characteristics of Supercritical Carbon Dioxide (SC-CO 2 ) Jet Fracturing in Limited Perforation Scenarios

Can Cai, Song Xie, Qingren Liu, Yong Kang, Dong Lian and Banrun Li
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Can Cai: School of Mechanical Engineering, Southwest Petroleum University, Chengdu 610500, China
Song Xie: School of Mechanical Engineering, Southwest Petroleum University, Chengdu 610500, China
Qingren Liu: Jianghan Mechinery Research Institute Limited Company of CNPC, Wuhan 430000, China
Yong Kang: School of Power and Mechanical Engineering, Wuhan University, Wuhan 430000, China
Dong Lian: Shandong High Speed Railway Construction Equipment Co., Ltd., Weifang 261000, China
Banrun Li: School of Mechanical Engineering, Southwest Petroleum University, Chengdu 610500, China

Energies, 2020, vol. 13, issue 10, 1-19

Abstract: Supercritical carbon dioxide (SC-CO 2 ) jet fracturing is a promising alternative for shale gas fracturing instead of water. However, most studies pay more attention to the fracture generation and ignore the flow characteristic of SC-CO 2 jet fracturing in limited perforation scenarios. To accurately explore the flow field in a limited perforation tunnel, a numerical model of a SC-CO 2 jet in a limited perforation tunnel before fracture initiation is established based on the corresponding engineering background. The comparison between the numerical simulation and experiments has proved that the model is viable for this type of analysis. By using the numerical method, the flow field of the SC-CO 2 jet fracturing is analyzed, and influencing factors are discussed later. The verification and validation show that the numerical model is both reliable and accurate. With the dramatic fluctuating of turbulent mixing in a fully developed region, there is an apparent increase in the CO 2 density and total pressure during limited perforation. When the z increases from 10 times r 0 to 145 times r 0 , the velocity on the perforation wall surface would decrease below 0 m/s, resulting in backflow in the perforation tunnel. The structure of the nozzle, including the outlet length and outlet diameters, significantly affects the axial velocity and boosting pressure in the perforation tunnel. The highest total pressure exists when the nozzle length-to-radius ratio is 2. The maximum velocity of the jet core drops from 138.7 to 78 m/s, and the “hydraulic isolating ring” starts disappearing when the radius changes from 1 to 1.5 mm. It is necessary to increase the aperture ratio as much as possible to ensure pressurization but not over 1. Based on a similar theory high-speed photography results clearly show that the SC-CO 2 develops to fully jetting in only 0.07 s and a strong mixing exists in the annular region between the jet core and the surroundings, according with the numerical simulation. This study should be helpful for scholars to comprehensively understand the interaction between the SC-CO 2 jet and perforation, which is beneficial for studying SC-CO 2 fracturing.

Keywords: supercritical carbon dioxide; jet fracturing; limited perforation; flow field (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2020
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