An adaptive multiphysics model coupling vertical equilibrium and full multidimensions for multiphase flow in porous media

TL;DR

This paper introduces an adaptive multiphysics modeling approach that couples vertical equilibrium and full multidimensional models for efficient and accurate simulation of multiphase flow in porous media, optimizing computational resources.

Contribution

The paper presents a novel adaptive coupling method that dynamically applies VE and full models based on a new criterion, enhancing efficiency without sacrificing accuracy.

Findings

Significant reduction in computational cost compared to full multidimensional models.

Maintains high accuracy in simulating gas injection scenarios.

Provides guidelines for optimal threshold parameter selection.

Abstract

Efficient multiphysics models that can adapt to the varying complexity of physical processes in space and time are desirable for modeling fluid migration in the subsurface. Vertical equilibrium (VE) models are simplified mathematical models that are computationally efficient but rely on the assumption of instant gravity segregation of the two phases, which may not be valid at all times or at all locations in the domain. Here, we present a multiphysics model that couples a VE model to a full multidimensional model that has no reduction in dimensionality. We develop a criterion that determines subdomains where the VE assumption is valid during simulation. The VE model is then adaptively applied in those subdomains, reducing the number of computational cells due to the reduction in dimensionality, while the rest of the domain is solved by the full multidimensional model. We analyze how the threshold parameter of the criterion influences accuracy and computational cost of the new multiphysics model and give recommendations for the choice of optimal threshold parameters. Finally, we use a test case of gas injection to show that the adaptive multiphysics model is much more computationally efficient than using the full multidimensional model in the entire domain, while maintaining much of the accuracy.