TY - JOUR
T1 - A fractal model for gas-water relative permeability in inorganic shale considering water occurrence state
AU - Yang, Rui
AU - Ma, Tianran
AU - Kang, Yulong
AU - Du, Hongzhou
AU - Xie, Shuli
AU - Ma, Depeng
N1 - Publisher Copyright:
© 2024 Elsevier Ltd
PY - 2025
Y1 - 2025
N2 - Gas-water relative permeability in inorganic shale plays a crucial role in fluid transfer efficiency, therefore it is of paramount importance for modelling shale gas recovery. This study introduces a novel theoretical model to determine gas–water relative permeability in inorganic shale under various water saturations. For the first time, this model integrates the water occurrence state in inorganic shale with the fractal characteristics of pore structures. In particular, three distinct states of water occurrence in inorganic shale pores and two corresponding critical pore sizes are defined in the model based on nuclear magnetic resonance (NMR) testing. The validity and accuracy of the new model have been corroborated by multiple sets of experimental data for shale and other porous rocks. Additionally, the model discussion focus on the water occurrence state in inorganic shale is conducted, and the following results are innovatively obtained: (1) Ignoring pores with only irreducible water results in a 6–26 % overestimation of gas relative permeability (GRP) and approximately 4 % overestimation of water relative permeability (WRP). (2) Omitting pores with both irreducible and movable water leads to a 2–13 % overestimation of GRP and a 1.1 to 21 times overestimation of WRP at various water saturations. (3) Disregarding pores with only movable water causes an approximately 23 % underestimation of GRP and a 13–100 % underestimation of WRP at different water saturations. Furthermore, based on the proposed model, the impact of fractal dimension of pore size distribution, fractal dimension of pore tortuosity, irreducible water saturation, and critical pore sizes are also comprehensively analyzed.
AB - Gas-water relative permeability in inorganic shale plays a crucial role in fluid transfer efficiency, therefore it is of paramount importance for modelling shale gas recovery. This study introduces a novel theoretical model to determine gas–water relative permeability in inorganic shale under various water saturations. For the first time, this model integrates the water occurrence state in inorganic shale with the fractal characteristics of pore structures. In particular, three distinct states of water occurrence in inorganic shale pores and two corresponding critical pore sizes are defined in the model based on nuclear magnetic resonance (NMR) testing. The validity and accuracy of the new model have been corroborated by multiple sets of experimental data for shale and other porous rocks. Additionally, the model discussion focus on the water occurrence state in inorganic shale is conducted, and the following results are innovatively obtained: (1) Ignoring pores with only irreducible water results in a 6–26 % overestimation of gas relative permeability (GRP) and approximately 4 % overestimation of water relative permeability (WRP). (2) Omitting pores with both irreducible and movable water leads to a 2–13 % overestimation of GRP and a 1.1 to 21 times overestimation of WRP at various water saturations. (3) Disregarding pores with only movable water causes an approximately 23 % underestimation of GRP and a 13–100 % underestimation of WRP at different water saturations. Furthermore, based on the proposed model, the impact of fractal dimension of pore size distribution, fractal dimension of pore tortuosity, irreducible water saturation, and critical pore sizes are also comprehensively analyzed.
KW - Fractal model
KW - Gas-water two phase
KW - Inorganic shale
KW - Relative permeability
KW - Water occurrence state
U2 - 10.1016/j.fuel.2024.133664
DO - 10.1016/j.fuel.2024.133664
M3 - Journal article
AN - SCOPUS:85208535047
SN - 0016-2361
VL - 381
JO - Fuel
JF - Fuel
M1 - 133664
ER -