Sub-grid models for multiphase fluid flow inside fractures in poroelastic media

Models have been developed for the simulation of multiphase fluid flow within fractured poroelastic media. They allow for the fluid phases to interact inside fractures, without requiring explicit simulations in the interior of the fractures. The models retain the ability to retrieve the fluid velocity profile in the fracture by post-processing. The models for flow within a fracture are combined with a formulation for multiphase flow within the poroelastic medium. They have been implemented using isogeometric analysis, cast into a traditional finite element format using Bézier extraction. Pressure oscillations around the fracture are prevented by using a lumped integration scheme for the pressure capacity. The effect of interactions between the fluid phases is first demonstrated for a single fracture through parameter studies. Next, two cases with a more practical orientation are simulated. They show, inter alia, that the inclusion of interactions between the fluid phases can result in fluid back-flow.