InterPore2021

A hybrid-dimensional compositional two-phase flow model in fractured porous media with phase transitions and Fickian diffusion

2 Jun 2021, 15:00

15m

Oral Presentation (MS7) Mathematical and numerical methods for multi-scale multi-physics, nonlinear coupled processes MS7

Speaker

Joubine Aghili (IRMA, Univ. Strasbourg)

Description

We consider an extension of Discrete Fracture Matrix (DFM) models to compositional two-phase Darcy flows in fractured porous media.
The model is hybrid-dimensional, i.e. fractures are treated as surfaces of co-dimension one, and accounts for phase transitions and Fickian diffusion. It is based on physically consistent transmission conditions across matrix fractures (m-f) interfaces resulting from flux continuity equations at interfaces and Two-Point Flux Approximations in the fracture width. They allow to capture saturation jumps for general capillary pressure laws as well as the Fickian diffusion in the fracture width and the thermodynamical equilibrium based on complementary constraints. DFM models introduced previously consider simplified transmission conditions at m-f interfaces classically obtained by jumping over the m-f interfaces in order to reduce the computational cost. However, we show that they are less accurate than our reduced model and leads, in some cases, to physically inconsistent solutions. Validation is made with a reference equi-dimensional model.
We will also show that the Fickian diffusion plays a crucial role on the gas transfer at the m-f interfaces. This point will be discussed and illustrated with two types of test cases both using a fluid system with liquid and gas phases defined as mixtures of air and water components. Finally, we investigate the desaturation by suction with a data set based on Andra nuclear waste storage prototype facility.