TY - JOUR
T1 - Investigation of Shale Permeability Evolution considering Bivalued Effective Stress Coefficients for CO2Injection
AU - Wang, Yi
AU - Wang, Hao
AU - Qi, Shangyi
AU - Liu, Shimin
AU - Zhao, Yixin
AU - Yue, Wenting
N1 - Publisher Copyright:
© 2021 Yi Wang et al.
PY - 2021
Y1 - 2021
N2 - Because of the existence of multiscale pores from nano- to macroscale, a multimechanistic shale gas flow process involving the Darcy and Knudsen flows occurs during gas shale well depletion. The respective contribution of the Darcy and Knudsen flows to the permeability is constantly changing with pressure evolution. In this study, laboratory measurements of shale permeability with CO2 injections were carried out under hydrostatic conditions, using the transient pulse-decay method. The "U"-shape permeability curve resulted in both positive and negative effective stress coefficients (Biot's coefficient) χ. A permeability turning point was thus created to partition permeability curves into the Darcy and Knudsen sections. The Knudsen effect was proven to be significant at low pressure/late time in the laboratory. Effective stress and sorption-induced deformation have been found to govern the Darcy permeability evolution under the tested experimental conditions. Thus, negative effective stress coefficients, together with the positive ones, should be applied to a nonmonotonic pressure-permeability evolution to explain the concurrent effect of the Darcy flow and Knudsen flow at different pore pressures.
AB - Because of the existence of multiscale pores from nano- to macroscale, a multimechanistic shale gas flow process involving the Darcy and Knudsen flows occurs during gas shale well depletion. The respective contribution of the Darcy and Knudsen flows to the permeability is constantly changing with pressure evolution. In this study, laboratory measurements of shale permeability with CO2 injections were carried out under hydrostatic conditions, using the transient pulse-decay method. The "U"-shape permeability curve resulted in both positive and negative effective stress coefficients (Biot's coefficient) χ. A permeability turning point was thus created to partition permeability curves into the Darcy and Knudsen sections. The Knudsen effect was proven to be significant at low pressure/late time in the laboratory. Effective stress and sorption-induced deformation have been found to govern the Darcy permeability evolution under the tested experimental conditions. Thus, negative effective stress coefficients, together with the positive ones, should be applied to a nonmonotonic pressure-permeability evolution to explain the concurrent effect of the Darcy flow and Knudsen flow at different pore pressures.
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U2 - 10.1155/2021/1132440
DO - 10.1155/2021/1132440
M3 - Article
AN - SCOPUS:85117321639
SN - 1468-8115
VL - 2021
JO - Geofluids
JF - Geofluids
M1 - 1132440
ER -