In this study, a newly developed threedimensional, fully implicit, finite element black oil simulation system for heterogeneous reservoirs with horizontal wells and vertical fractures is presented. This simulation system utilizes an efficient and almost fully automatic three-dimensional finite element grid generation technique with natural grid refinement capabdities around wells and fractures. The region between the well/fracture system and the outer boundary is gridded by an automatic tettahedronization scheme such that selective refinement and accurate representation of heterogeneities are achieved. The result is a fine and well graded grid based on expected flow patters around the well/fiacture system.

In this simulation system the wellbore is tteated as a hollow tube. The multi-phase black oil flow within fractures is accurately modeled including variable fracture conductivity. Furthermore fracture and reservoir flow equations are analyticaly coupled utilizing continuity of fluxes at the domain interfaces. This allows easy application of established black oil simulation techniques to reservoirs with horizontal wells and vertical fractures.

The use of the model is demonstrated in simulating waterflooding in a square reservoir using one horizontal injection well and two vertical production wells. The model seems to produce accurate numerical results almost free of grid orientation effects.

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