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This contribution describes HEX, a computer tool for integrated fluvial architecture modelling and simulation of recovery processes, using hexagonal grid systems. Stochastic modelling of a system of intersecting channel sands deposited in a braided stream environment is described. An hexagonal sub-division of the model plane is used to discretize fluvial sand bodies. The same hexagonal grid is used for subsequent reservoir simulation, and thus the simulation model produced is a clear representation of the geological model of the reservoir. The derivation of intercell transmissibilities is described together with the use of non-neighbour connections between grid cells. This conventiently enables the model to be run using a conventional (Cartesian) simulator. Examples are presented of simulation studies of water-oil displacement in a reservoir in which the effect of permeability heterogeneity in the reservoir is investigated, together with the effect of lateral barriers to flow, along the channel banks. An example of matching pressure behaviour of a long-term production and build-up test is given, using a stochastic reservoir model generated by HEX, in which the deterministic parameters of three wells were honoured. The use of a hexagonal grid overcomes the problems of grid-orientation effects and allows accurate modelling of fluid flow both diagonal and parallel to the principal grid directions. The technique is straightforward to use and enhances the capacity to plan the development of complex fluvial reservoirs. |
