Abstract
In the development of tight gas reservoirs, gas flow through porous media usually takes place deep underground with multiple mechanisms, including gas slippage and stress sensitivity of permeability and porosity. However, little work has been done to simultaneously incorporate these mechanisms in the lattice Boltzmann model for simulating gas flow through porous media. This paper presents a lattice Boltzmann model for gas flow through porous media with a consideration of these effects. The apparent permeability and porosity are calculated based on the intrinsic permeability, intrinsic porosity, permeability modulus, porosity sensitivity exponent, and pressure. Gas flow in a two-dimensional channel filled with a homogeneous porous medium is simulated to validate the present model. Simulation results reveal that gas slippage can enhance the flow rate in tight porous media, while stress sensitivity of permeability and porosity reduces the flow rate. The simulation results of gas flow in a porous medium with different mineral components show that the gas slippage and stress sensitivity of permeability and porosity not only affect the global velocity magnitude, but also have an effect on the flow field. In addition, gas flow in a porous medium with fractures is also investigated. It is found that the fractures along the pressure-gradient direction significantly enhance the total flow rate, while the fractures perpendicular to the pressure-gradient direction have little effect on the global permeability of the porous medium. For the porous medium without fractures, the gas-slippage effect is a major influence factor on the global permeability, especially under low pressure; for the porous medium with fractures, the stress-sensitivity effect plays a more important role in gas flow.
Highlights
Gas flows in tight porous media have recently attracted much attention because they are widely applied in engineering fields, such as oil-gas field development, chemical processes, new energy development, and so on
In a porous medium is the smallest volume at which the scale characteristics of the porous flow hold, and the flow in a porous medium can be simulated at the representative elementary volume (REV) scale without detailed information of the pore structures
Gas flow in a channel filled with a homogeneous porous medium is simulated to validate the present lattice Boltzmann (LB) model
Summary
Gas flows in tight porous media have recently attracted much attention because they are widely applied in engineering fields, such as oil-gas field development, chemical processes, new energy development, and so on. The wide applications of gas flows in tight porous media stimulate great interest in experimental and theoretical studies [1,2,3,4,5,6,7,8,9,10,11,12,13]. An REV in a porous medium is the smallest volume at which the scale characteristics of the porous flow hold, and the flow in a porous medium can be simulated at the REV scale without detailed information of the pore structures. Recently, many REV-scale models have been proposed in the literature, such as the Darcy model, extended Darcy models (including Brinkman-extended Darcy and Forchheimer–Darcy models), and generalized model based on the generalized Navier–Stokes equations
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