Capturing reservoir heterogeneity in a sand-rich submarine fan, Miller Field

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Miller production began its decline phase in July 1997. To investigate the challenges of the decline period and the options for extending field life a detailed reservoir heterogeneity model was set up based on analysis of 26 wells, of which 19 were cored. The Miller fan is a high net: gross sandy submarine fan system in which lobe abandonment facies and numerous thin shales form the important heterogeneities. Each reservoir zone was described in terms of eight depositional elements and fourteen lithotypes. These descriptions were incorporated into the model at a resolution which ensured capture of the most significant heterogeneities. A stochastic generator was used to build a detailed static description of the permeability of the reservoir. The important heterogeneities were captured in a cell size of 60 m × 60 m × c. 0.02 m. Volumetric rock properties such as zone isochore, net: gross and porosity were mapped using conventional methods. The static description was up-scaled into an area of local grid refinement of the Eclipse reservoir simulator with 33 dynamic subzones at a cell size of 100 m × 100 m × c. 2.5 m. The detailed reservoir model matched well and field performance in the decline period more closely than the previous deterministic model. Stochastic realizations of the model enabled a better estimate of uncertainty to be demonstrated. The success of the process indicated that greater benefit would be obtained by its extension over a larger area of the field.