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Appl. Sci. 2018, 8(7), 1092; https://doi.org/10.3390/app8071092

Comparison of CO2 Flow Behavior through Intact Siltstone Sample under Tri-Axial Steady-State and Transient Flow Conditions

1
Deep Earth Energy Laboratory, Department of Civil Engineering, Monash University, Building 60, Melbourne, VIC 3800, Australia
2
Department of Infrastructure Engineering, The University of Melbourne, 209B, Building 175, Melbourne, VIC 3010, Australia
*
Author to whom correspondence should be addressed.
Received: 20 March 2018 / Revised: 8 June 2018 / Accepted: 27 June 2018 / Published: 5 July 2018
(This article belongs to the Special Issue The Applications of Supercritical Carbon Dioxide)

Abstract

With its low viscosity properties, CO2 has much greater penetration capacity into micro-fractures, and therefore has more potential to create expanded and effective fractures in shales during the hydraulic fracturing process. However, the feasibility of this technique is dependent on the accurate prediction of formation flow characteristics, given the high leak-off of CO2 at deep depths. The aim of this study is therefore to understand the flow behavior of CO2 in deep shale plays. A series of tri-axial permeability tests was conducted under both steady-state and transient conditions. The test results show much lower permeability values for liquid CO2 than gaseous CO2, and the permeability under transient conditions is much lower than that under steady-state conditions, due to the combined effects of the reduced slip-flow effect under low pressures and the temperature variation influence under steady-state conditions. Under steady-state conditions, unstable flow behavior occurred at higher injection pressure (≥9 MPa) possibly due to the fine mineral particle migration and the deposition of small drikold particles, which indicates the serious error in permeability calculation under steady-state conditions. Importantly, a greater than 1 effective stress coefficient (χ) for permeability in tested siltstone was observed, confirming the greater sensitivity of CO2 to pore pressure than confining pressure. View Full-Text
Keywords: CO2 apparent permeability; CO2 phase transition; siltstone; steady-state conditions; transient conditions CO2 apparent permeability; CO2 phase transition; siltstone; steady-state conditions; transient conditions
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Zhang, C.; Pathegama Gamage, R.; Anne Perera, M.S. Comparison of CO2 Flow Behavior through Intact Siltstone Sample under Tri-Axial Steady-State and Transient Flow Conditions. Appl. Sci. 2018, 8, 1092.

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