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This paper presents a meshing algorithm for domains with internal boundaries. It is an extension of the gridding algorithm presented by Persson and Strang. The resulting triangulation matches all boundaries, and the triangles are all nearly equilateral. Equilateral triangles are beneficial for a finite volume discretization, as fluid flow between elements of very different size is only possible at small timesteps. The mesh generator is compared with the well regarded Triangle programme, where both element quality and simulation performance are checked. It is shown that our mesh generator consistently delivers better meshes.

When regions of three-phase flow arise in an oil reservoir, each of the flow parameters, i.e. capillary pressures and relative permeabilities, are generally functions of two phase saturations and depend on the wettability state. The idea of this work is to generate consistent pore-scale based three-phase capillary pressures and relative permeabilities. These are then used as input to a 1-D continuum core-or reservoir-scale simulator. The pore-scale model comprises a bundle of cylindrical capillary tubes, which has a distribution of radii and a prescribed wettability state. Contrary to a full pore-network model, the bundle model allows us to obtain the flow functions for the saturations produced at the continuum-scale iteratively. Hence, the complex dependencies of relative permeability and capillary pressure on saturation are directly taken care of. Simulations of gas injection are performed for different initial water and oil saturations, with and without capillary pressures, to demonstrate how the wettability state, incorporated in the pore-scale based flow functions, affects the continuum-scale displacement patterns and saturation profiles. In general, wettability has a major impact on the displacements, even when capillary pressure is suppressed. Moreover, displacement paths produced at the pore-scale and at the continuum-scale models are similar, but they never completely coincide.

Usually extended two-phase capillary pressures are used in three-phase simulations, because three-phase capillary pressures are not possible or hard to measure. In this work three-phase capillary pressure surfaces are created by at pore network model. The input parameters to this network model are found by matching two-phase capillary pressure curves. This matching is done with a slightly modified EnKF routine. Tables with three-phase capillary pressures are created and used as input to flow simulations.

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