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The Pathway‐Flow Relative Permeability of CO 2 : Measurement by Lowered Pressure Drops
Author(s) -
Zhang Yi,
Nishizawa Osamu,
Park Hyuck,
Kiyama Tamotsu,
Lei Xinglin,
Xue Ziqiu
Publication year - 2017
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1002/2017wr020580
Subject(s) - relative permeability , pressure drop , permeability (electromagnetism) , volumetric flow rate , saturation (graph theory) , flow coefficient , mechanics , materials science , supercritical fluid , drop (telecommunication) , chemistry , thermodynamics , composite material , mathematics , physics , porosity , engineering , combinatorics , telecommunications , biochemistry , membrane
We introduce a simple method to measure the relative permeability of supercritical CO 2 in low‐permeability rocks. The method is built on the assumption of the stability of formed CO 2 percolation pathway under lowered pressure drops. Initially, a continuous CO 2 flow pathway is created under a relatively high‐pressure drop. Then, several subsequent steps of lowered pressure drops are performed while monitoring the associated flow rates. When the pressure drop is lower than a threshold value, the created flow pathway is assumed to be adequately stable and does not vary significantly during successive flows, with the average saturation and flow rate achieving a quasi steady state. The relative permeability of CO 2 is then calculated from the relationship between the pressure drop and flow rate at several lowered pressure drops according to the extended form of Darcy's law. We demonstrate this method using both numerical modeling and an experimental test using X‐ray CT imaging. The results indicate the validity of the assumption for the stability of flow pathway under lowered pressure drops. A linear relationship between the lowered pressure drops and the corresponding CO 2 flow rate is found. Furthermore, the measurement results suggest that the relative permeability of CO 2 can still be high in low‐permeability rocks if the CO 2 saturation is higher than the threshold value required to build a flow pathway. The proposed method is important for measuring the pathway‐flow relative permeability of nonwetting fluids in low‐permeability rocks.