HR: 1340h
AN: H13C-1392    [Abstracts]
TI: Pore-scale modelling of two-phase and three-phase fracture-matrix interface conditions
AU: Abdev, J
EM: joseph.abdev@pet.hw.ac.uk
AF: Institute of Petroleum Engineering, Heriot-Watt University, Edinburgh, EH14 4AS, United Kingdom
AU: * Geiger, S
EM: sebastian.geiger@pet.hw.ac.uk
AF: Institute of Petroleum Engineering, Heriot-Watt University, Edinburgh, EH14 4AS, United Kingdom
AU: Van Dijke, R
EM: rink@pet.hw.ac.uk
AF: Institute of Petroleum Engineering, Heriot-Watt University, Edinburgh, EH14 4AS, United Kingdom
AB: A key assumption of multi-phase discrete fracture model simulations is that the capillary pressure is constant and continuous at nodes that are shared by the fracture as well as by the matrix. In this work, we study the fundamental flow physics at the fracture-matrix interface using a 3D pore-scale network model. The conceptual model represents the pores of the matrix and fracture for the situation where the fluid flow is perpendicular to the interface plane, hence mimicking counter-current imbibition. We could not validate the general assumption that the capillary pressure at the interface is continuous directly. Instead it was inferred from the study of the flow pattern across it. By determining the capillary pressure curves individually for the fracture and matrix individually and comparing it with the capillary pressure of the heterogeneous fracture-matrix interface, we were able to develop a qualitative understanding of the trapping behaviour and the residual phase saturations. In general, our simulations show how the wetting phase fills preferentially the smallest pores while the non-wetting phase fills the largest pores. However, the heterogeneity at the fracture-matrix interface gives rise to complex new capillary pressure curves that cannot be modeled by classical Brooks-Corey or van Genuchten curves. We observed that hysteresis effects increase with increasingly more heterogeneous the media. This implies that two different capillary pressure curves should be used for drainage and imbibition.
DE: 1828 Groundwater hydraulics
DE: 1849 Numerical approximations and analysis
DE: 8010 Fractures and faults
SC: Hydrology [H]
MN: 2007 Fall Meeting