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Description
Comprehensive Analysis and Modeling of Gas Slippage Effects Governing Permeability in Tight Porous Media for H2 and CO2 storage
Objectives/Scope:
This paper aims to critically evaluate and classify gas slippage models for predicting permeability in tight and nanoporous formations. It investigates first-order, second-order, and non-ideal gas flow behaviours, with a focus on the impact of pressure, pore structure, and gas properties. The study integrates stress-dependent permeability and slippage modelling to improve accuracy in estimating gas flow in tight reservoirs.
Methods, Procedures, Process:
The analysis is based on a comprehensive dataset of 138 gas permeability tests compiled from nine published sources, encompassing clastic, coal, and carbonate lithologies. Models were categorized according to their handling of viscous flow, Knudsen diffusion, and real gas effects. First-order (Klinkenberg), second-order (Knudsen and velocity profile), and non-ideal gas models (using virial coefficients and cubic equations of state) were systematically applied and compared. Stress sensitivity and pseudo-Knudsen scaling were also incorporated to simulate effective permeability under field-relevant conditions. Model accuracy was validated using well inflow performance calculations for various reservoir and gas types.
Results, Observations, Conclusions:
Results confirm that Klinkenberg’s first-order correction remains reliable at moderate pressures but overestimates permeability in ultra-tight formations or with non-ideal gases. Second-order slippage models offer improved accuracy, especially under nanopore flow conditions. Non-ideal gas models, incorporating temperature- and pressure-dependent virial coefficients, further refine predictions in complex gas systems (e.g., H2, CO₂, hydrocarbons). When applied to vertical well inflow performance, improper model selection caused permeability and productivity overpredictions of up to 20%. Stress-dependent effects further reduced permeability at high confining pressures, counteracting slippage gains. The integrated modeling framework accounts for lithology, fluid type, pore size, and stress, and supports more realistic forecasts of tight reservoir performance.
Novel/Additive Information:
This paper provides a unified modelling workflow that bridges empirical testing and theoretical models, incorporating non-ideal gas behaviour and stress effects. It extends current understanding of permeability prediction under complex subsurface conditions, offering guidance for selecting appropriate slippage models for various tight gas systems. The approach is directly applicable to reservoir engineering, production forecasting, and core analysis workflows.
| Country | Saudi Arabia |
|---|---|
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