Prediction of fluid occupancy in fractures using network modeling and x-ray microtomography. II: Results

This paper presents the implementation of the pore-scale network model described in paper I [see preceding paper, Z. T. Karpyn and M. Piri, Phys. Rev. E 76, 016315 (2007)]. The model is used to estimate flow properties and predict fluid occupancy during two-phase flow displacements in a rough-walled fracture. The fracture's inner structure is available from the reconstruction of x-ray microtomography images of a fractured sandstone core. The model is able to represent mechanisms such as pistonlike displacement, cooperative pore filling, and snapoff. We study the effects of aperture map scales, rate of injection, and gravity on the distribution of phases inside the fracture and present successful predictions of fluid occupancy during primary drainage, imbibition, and secondary drainage. Results were validated rigorously against x-ray microtomography scans obtained from two-phase flow experiments [see Z. T. Karpyn, A. S. Grader, and P. M. Halleck, J. Colloid Interface Sci. 307, 181 (2007)] and showed two-phase fluid structures in agreement with experimental observations.