Three-dimensional geological modelling and reservoir simulations of an outcrop analogue to reservoirs of the Halten Terrace, offshore mid-Norway, are presented. The model of the outcrop incorporates (a) a detailed sedimentological understanding, (b) a set of stochastic realizations highly-constrained to the geological models and (c) streamline waterflood flow simulations assuming typical subsurface petrophysical properties from the Halten Terrace. Statistical analysis of simulation results has been used to show the importance of both the facies architecture and the spatial petrophysical model. The outcrop model has significantly improved the estimation of facies dimensions and architecture and gives a valuable insight into understanding petroleum reservoirs of the Halten Terrace.

This study concerns the modelling of complex tidal heterogeneities found in the Lower Jurassic Tilje Formation offshore mid-Norway. The Tilje Formation is characterized by tidal channels, tidal bars (shoals), tidal flats and deltaic deposits. The lithofacies associations have been modelled as large-scale objects with a wide range of shapes (channels, sheets and lobes). In addition small-scale models of the internal bedding structure have been generated in order to calculate effective permeability values at appropriate modelling scales. In order to assess the influence of the static input factors on recovery predictions, several production response variables were recorded for each of the 120 realizations generated. These include: streamline densities, breakthrough time measured in movable pore volume injected, pore volume tracer injected at 50% and 95% tracer fraction in the producer, and recovery factor of movable pore water at 95% tracer fraction in the producer. For this purpose we used a streamline reservoir simulator (Frontsim) with a tracer option (single-phase flow simulations). By using analysis of variance, we identified the following parameters which have the largest influence on single-phase fluid flow: (1) dimension of large-scale bar objects; (2) effective permeabilities of marginal (background) facies; and (3) interaction effects between bar objects and background permeabilities. In addition, the effective permeability values of the marginal facies are highly controlled by certain thresholds in mud content.

TX 75083-3836, U.S.A., fax 01-972-952-9435. SummaryThe Smørbukk Field comprises a deep, very heterogeneous reservoir with variable fluids (gas condensate to light oil). This study presents a series of sensitivity studies to evaluate the effect of different geological parameters and development options on oil production and gas oil ratio within a sector of that field. The black-oil Eclipse reservoir simulator is used to represent the gas displacing oil behavior of this rather complex reservoir. Constant production rates and pressure controls are assumed. Detailed geological models of sedimentary and structural heterogeneity were used to define reservoir simulation models with upscaled permeabilities and relative permeabilites. Displacement and transmissibility reduction across faults were explicitly modeled and compared with simpler assumptions. The main performance measure used is oil recovery and GOR at the five year production point. Important interactions between geological assumptions and fluid rates and pressures were identified and used to identify the most promising production strategy.

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