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A wellbore flow model and coupling solution for supercritical CO2 fracturing |
LI Xiaojiang, LI Gensheng, WANG Haizhu, TIAN Shouceng, SONG Xianzhi, LU Peiqing, LIU Qingling1,2
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1. State Key Laboratory of Petroleum Resource and Prospecting in China University of Petroleum, Beijing 102249, China;2. Research Institute of Petroleum Engineering, SINOPEC, Beijing 100101, China
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Abstract: |
Supercritical carbon dioxide (CO2) can be applied as a new type of non-aqueous fracturing fluid. Precise prediction of the bottomhole temperature and pressure is the key requirement for the design and operation of supercritical CO2 fracturing. In this paper, a theoretical CO2 wellbore flow model was developed based on the conservation laws of mass, momentum and energy balance. The equation of state for CO2 proposed by Span and Wagner and a model proposed by Fenghour et al. were adopted to calculate the in-situ thermodynamic and transport properties of CO2 at wellbore conditions. The model was solved by coupling pressure and temperature along the wellbore and coupling tubing-annulus-formation in the radial direction. The derivation of the model was validated by comparing with the classical models, and the accuracy of model was verified using data from a CO2 injection well, in which the relative errors are below 1%. The results indicate that heat generated by gas expansion or compression should be considered in the process of CO2 injection at a low rate. Moreover, the heat generated by gas expansion and friction should be considered for the CO2 fracturing at high injection rates, while the Joule-Thompson effect can be neglected at most operating conditions. |
Key words: supercritical CO2 fracturing wellbore flow model coupling solution heat source/sink |
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