Pore-scale simulation of miscible viscous fingering with dissolution reaction in porous media

Timan Lei,Kai H Luo

doi:10.1063/5.0045051

Abstract

Global climate change is happening but may be mitigated by the technology of geological carbon dioxide (CO2) sequestration. To gain comprehensive insights into this approach, we perform pore-scale simulations of displacement between two miscible fluids in porous media using a new multiple-relaxation-time lattice Boltzmann model. This study marks the first attempt to investigate viscous fingering dynamics in miscible displacement, considering the coexistence of viscosity contrast and dissolution reaction. Simulation results capture different fingering patterns that depend on dissolution (Damköhler number Da), diffusion (Peclet number Pe), and viscosity contrast (viscosity ratio R). From simulations of unstable viscous flows, dissolution is found to delay fingering onset, slow down fingering propagation, and inhibit or reinforce the late-stage fingering intensity. In simulations with stable viscosity contrasts, the displacement features fingering phenomena when dissolution is fast enough. In addition, we conduct a parametric study to assess the impact of Pe, R, and Da. The results suggest that increasing Pe or R destabilizes fingering, but increasing Da first suppresses and gradually intensifies fingering. Finally, for every fixed Da, we determine the phase boundary between stable and unstable regimes in a Pe–R phase plane. A unified scaling law is developed to approximate boundary lines obtained under different Da values. By comparing reactive and nonreactive cases, we classify four distinct regimes: stable, unstable, reactive stable, and reactive unstable. These pore-scale insights are helpful in understanding and predicting the displacement stability during the geological CO2 sequestration, which is of importance to the pre-evaluation of the storage efficiency and safety.

Highlights

Global climate change is associated with the growing carbon dioxide (CO2) emission to the atmosphere, thereby directing efforts toward limiting the anthropogenic CO2 emission
In regard to boundary conditions, the top and bottom boundaries are periodic, zero-gradient conditions are applied for all the scalars at the outlet, and the fixed viscosity and concentration of fluid 1 are employed at the inlet
Based on a new multiple-relaxation-time reactive lattice Boltzmann model, pore-scale simulations of miscible displacement between two fluids have been performed in a homogeneous porous medium

Summary

INTRODUCTION

Global climate change is associated with the growing carbon dioxide (CO2) emission to the atmosphere, thereby directing efforts toward limiting the anthropogenic CO2 emission. The reaction consumes chemical solutes and dissolves solid matrices, which increases media porosity (fluid mobility) behind the moving interface.[3] Such mineral dissolutions make a fluid in a high-mobility area displace another fluid in a lowmobility zone, thereby triggering fingering phenomena ( known as infiltration instability).[17,18]. These existing studies have enriched our knowledge about miscible fingering instability induced by viscosity contrast or dissolution reaction in porous media They were carried out at the macroscopic scale, obtaining effective transport and reactive parameters via empirical correlations or volume-averaged techniques. To the best of our knowledge no pore-scale study has been devoted to investigating fingering dynamics considering the coexistence of viscosity contrast and chemical dissolution In applications such as long-term CO2 sequestration, these two factors usually take place simultaneously and have significant effects on viscous fingering instability.

RESULTS AND DISCUSSION

General viscous fingering patterns

Effects of Da

CONCLUSIONS

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