Modeling and Flow Simulations of a North Sea Turbidite Reservoir: Sensitivities and Upscaling

We have created a variety of detailed geological models, in order to carry out a sensitivity study in a turbidite oil reservoir. The base case stochastic model was generated using well-log data, seismic attribute data and information from outcrop analogues. In addition, some small-scale models were created to capture the effects of fine sedimentary structure (mudstone intra-clasts, and interbedded sandstone and mudstone layers). The main focus of this paper is on the flow simulation, upscaling and sensitivity analysis, rather than on the geological modelling. We carried out a range of sensitivity studies on two-phase flow parameters, gridding effects and upscaling. Our results show that the large-scale geological structure is potentially dominant. Integration of seismic information and the definition of zone transitions is crucial if an adequate history match is to be obtained. Redistributing the facies by successive realisations also impacted strongly on the productivity. The dominant two-phase flow property was wettability, particularly the shape of the capillary pressure curve, which could lead to a large capillary transition zone. In this particular field, the fine-scale structure, as modelled for two genetic units, did not have a large impact on the results, because these units occurred in isolated regions and were largely by-passed. Small scale heterogeneity in the main Channel Sandstone genetic unit did impact on flow, however.