An Apparent Permeability Model in Organic Shales: Coupling Multiple Flow Mechanisms and Factors.

Area of Science:

• Petroleum Engineering
• Geosciences
• Chemical Engineering

Background:

• Shale reservoirs exhibit complex pore structures and multiple flow mechanisms.
• Accurate modeling of shale apparent permeability is vital for reservoir characterization and production.

Purpose of the Study:

• To develop a new shale apparent permeability model incorporating confinement effects and thermodynamic properties.
• To investigate the influence of microscale phenomena on gas transport in shale.

Main Methods:

• Modified thermodynamic properties of gas and conservation of energy law to characterize bulk gas transport velocity.
• Assessed dynamic pore size changes to derive the apparent permeability model.
• Validated the model using experimental, molecular simulation, and laboratory shale data.

Main Results:

• Microscale effects significantly enhance gas permeability under low pressure and small pore sizes.
• Surface diffusion, matrix shrinkage, and real gas effects are prominent in smaller pores, while stress sensitivity dominates larger pores.
• Shale apparent permeability is influenced by material constants related to permeability, porosity, and internal swelling.

Conclusions:

• The developed model accurately predicts shale apparent permeability by accounting for various physical phenomena.
• Understanding microscale effects is critical for accurate gas transport prediction in shale reservoirs.
• The findings are essential for the numerical simulation and prediction of apparent permeability in shale formations.