Impact of Microscopic NAPL-Water Interface ...

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XVI International Conference on Computational Methods in Water Resources (CMWR-XVI) Ingeniørhuset

Impact of Microscopic NAPL-Water Interface Configurations on Subsequent Gas Injection into Water-Wet Permeable Rocks
Author:Ahmed Al-Futaisi <> (Department of Civil & Architectural Engineering, Sultan Qaboos University)
Tad Patzek <> (Department of Civil & Environmental Engineering, UC Berkeley)
Presenter:Ahmed Al-Futaisi <> (Department of Civil & Architectural Engineering, Sultan Qaboos University)
Date: 2006-06-18     Track: Special Sessions     Session: Pore-Scale Modelling: New Developments And Applications

Predictive field-scale models of the concurrent flow of three fluids require accurate predictions of five macroscopic flow descriptors: three relative permeabilities and two capillary-pressures as functions of the fluid saturations and saturation history. Since direct measurement of these descriptors is very difficult, and empirical correlations are often unreliable, the use of physically- based pore-scale models has become an appealing alternative. In this paper, we describe the features of our quasi-static pore network model for three immiscible fluids. The model integrates a realistic representation of pore connectivity and morphology reconstructed from 3D micro-focused X-ray CT images, a realistic description of fluid displacement mechanisms, and a sound representation of the wetting properties of the rock. All pore-level displacement mechanisms: piston- type, snap-off, cooperative pore-body filling, and double-displacements are considered with arbitrary contact angles and spreading coefficients. The proposed model is used to simulate gas injection into water-wet permeable rocks that initially contain water and NAPL after two-phase drainage followed by two-phase imbibition. The gas injection is performed using a cluster-based invasion percolation algorithm with trapping. The strong influence of the two-phase saturation history on the three-phase transport properties of a permeable rock is illustrated by performing a series of gas injections into Bentheimer and Berea sandstones with different initial NAPL and water saturations, and different microscopic fluid interface configurations.