A simulation method and system for complex boundary micro-flow

Abstract

The invention discloses a simulation method and a system for complex boundary micro-flow, comprising the following steps: 1) based on a lattice Boltzmann method, establishing a micro-scale flow modeland obtaining an initial distribution function; 2) obtaining a first distribution function after that interaction between the molecule and a second distribution function after the interaction betweenthe molecules and the boundary based on the initial distribution function; 3) obtaining the macroscopic parameters and the equilibrium distribution function require in the next time step internal collision migration process based on the first distribution function and the second distribution function; 4) determining the convergence of the lattice Boltzmann method, and if it is determined that theconvergence of the lattice Boltzmann method is not carried out, the steps 3-4 are repeated until the convergence calculation is terminated. Compared with the existing LBM model for calculating micro-scale flow, the present invention can process cases with complex structure boundary conditions while satisfying physical reality and accuracy, and the model is more concise and has smaller algorithm complexity and calculation amount.

Description

technical field [0001] The invention belongs to the field of tight gas and shale gas development, and more particularly relates to a simulation method and system for complex boundary micro-flow. Background technique [0002] Compared with conventional oil and gas reservoirs, shale reservoirs have extremely low matrix permeability, and shale gas reservoirs have different gas characteristics, physical properties and mechanical properties. The multi-scale migration mechanisms of shale gas mainly include: molecular-scale Knudsen diffusion inside and on the surface of kerogen, rarefied gas flow in shale micro- and nano-scale pores, and conventional viscous flow in macro-scale large fractures. Then, a deep understanding of the multi-scale migration mechanism in the process of shale gas exploitation is of great significance for the effective exploitation of shale gas and the establishment of an efficient "well factory" development model. [0003] Nano-scale pores are the main stor...

AI Technical Summary

Problems solved by technology

Although the probability of collision between methane gas molecules is still greater than the probability of collision with the solid surface, the momentum and energy exchange of the gas molecules after the collision at the solid surface is not complete at this time, resulting in the velocity and temperature of the gas on the solid surface and the boundary Different, resulting in speed slip and temperature jump

The Navier-Stokes equation can still describe the changes in the flow field and temperature field in this region, but it needs to use the boundary conditions of velocity slip and temperature jump for correction calculation

[0006] (3) Transition flow (Transition flow, 0.1<Kn<10), the probability of collision between methane gas molecules is equivalent to the probability of collision between gas molecules and solid surface, so the Navier-Stokes equation under the assumption of continuous medium is not then apply

However, the above three types of models are only suitable for simple two-dimensional straight channels, and cannot achieve accurate simulation calculations for micro-scale flows in porous structures with complex boundaries (such as tight shale, tight sandstone, etc.)

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