Limitations of Lattice Boltzmann Modeling of Micro‐Flows in Complex Nanopores

Abstract

The multiscale transport mechanism of methane in unconventional reservoirs is dominated by slip and transition flows resulting from the ultra‐low permeability of micro/nano‐scale pores, which requires consideration of the microscale and rarefaction effects. Traditional continuum‐based computational fluid dynamics (CFD) becomes problematic when modeling micro‐gaseous flow in these multiscale pore networks because of its disadvantages in the treatment of cases with a complicated boundary. As an alternative, the lattice Boltzmann method (LBM), a special discrete form of the Boltzmann equation, has been widely applied to model the multi‐scale and multi‐mechanism flows in unconventional reservoirs, considering its mesoscopic nature and advantages in simulating gas flows in complex porous media. Consequently, numerous LBM models and slip boundary schemes have been proposed and reported in the literature. This study investigates the predominately reported LBM models and kinetic boundary schemes. The results of these LBM models systematically compare to existing experimental results, analytical solutions of Navier‐Stokes, solutions of the Boltzmann equation, direct simulation of Monte Carlo (DSMC) and information‐preservation DSMC (IP_DSMC) results, as well as the numerical results of the linearized Boltzmann equation by the discrete velocity method (DVM). The results point out the challenges and limitations of existing multiple‐relaxation‐times LBM models in predicting micro‐gaseous flow in unconventional reservoirs.

Pore Size Dependence of Permeability in Bicontinuous Nanoporous Media

“…Our well-defined bicontinuous model is useful to characterize the effect of average pore sizes in the flow properties, ruling out other geometrical features. Other simplified models, such as single cylindrical pores, or systems with circular and square-shaped pore channels are also widely used for understanding the flow properties in the nanoporous system. To rule out the possible dependence of results on the specific nanoporous morphologies used, we use the same nanoporous morphology template in all systems.…”

“…Modeling methods can be very useful, yet they have their limitations. While continuum-scale simulations might not be able to capture the physical and chemical behavior of fluid particles in nanoporous media, , atomistic simulations are often limited by their small length and time scales. As a compromise, the dissipative particle dynamics (DPD) method, a mesoscale model originally introduced by Hoogerbrugge and Koelman, can bridge the length and time scale gap between continuum and atomistic simulations.…”

Pore‐scale study of reactive transfer process involving coke deposition via lattice Boltzmann method

“…33 Furthermore, the skeleton line method and the maximum circle method are employed to obtain the local pore diameter. 34,35 The skeleton line of the porous medium is first obtained, as shown in Figure 1E. The closest distance between the skeleton point and each solid point is identified as the characteristic length.…”

“…Then four connected regions marking the algorithm are applied so that the isolated pore can be removed 33 . Furthermore, the skeleton line method and the maximum circle method are employed to obtain the local pore diameter 34,35 . The skeleton line of the porous medium is first obtained, as shown in Figure 1E.…”

A single‐step and simplified graphics processing unit lattice Boltzmann method for high turbulent flows

“…It is well known that the LBM in its original form is generally limited to cases with low Reynolds and Mach numbers. 16 However, the potential of the LBM method can be greatly enhanced if coupled with a LES turbulence model.…”