High-resolution Numerical Modelling to Resolve the Dynamics of Pipe Structures in Porous Media

Common features visible on a large majority of the seismic cross sections are chimneys or pipe structures. They represent regions of focused fluid flow in porous media. As seismic surveys are widely performed in many regions where the subsurface is of economic interest, a better understanding of the formation and evolution process of these chimneys is vital. They should be considered when performing risk assessment linked to leakage within subsurface waste storage projects. They might also lead to a better understanding of fluid migration pathways and subsurface fluid localization. In that context, we propose a new physical model that predicts the formation and the evolution in space and time of these chimneys. We use a two-dimensional (2D) implicit solver and the three-dimensional (3D) high-resolution iterative parallel GPU code to solve a thermodynamically consistent system of nonlinear equations for two-phase flow in deforming porous media. We will show that the different 2D implicit and 3D iterative methods used to solve the fully coupled system of nonlinear equations are in good agreement. They predict the formation and the propagation of a nonlinear solitary wave, resulting in a chimney formation. These chimneys, with order of magnitude permeability increase, are a natural outcome of an interplay between buoyancy forces driving upward fluid propagation and a resistance of a deformable rock to locally increasing fluid pressure. We will also discuss and highlight the importance of a proper coupling between the geomechanics (Stokes solver) and the reservoir fluid flow (nonlinear Darcy solver).