--> ABSTRACT: 3-D Reservoir Modeling of Middle Jurassic Gilbert-Delta Complexes in the Oseberg Formation at the Giant Oseberg Oil Field, Viking Graben, Norwegian North Sea, by Kristian Soegaard, Ivar Lorentzen, Jos Anton Okkerman, Hans B. Helle, and Alpana Bhatt; #90906(2001)

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Kristian Soegaard1, Ivar Lorentzen1, Jos Anton Okkerman1, Hans B. Helle1, Alpana Bhatt2

(1) Norsk Hydro, Bergen, Norway
(2) Norwegian Univ. of Sci. and Tech, Trondheim, Norway

ABSTRACT: 3-D Reservoir Modeling of Middle Jurassic Gilbert-Delta Complexes in the Oseberg Formation at the Giant Oseberg Oil Field, Viking Graben, Norwegian North Sea

A detailed 3D reservoir model is developed for the Oseberg Formation at the giant Oseberg oil field in the Norwegian North Sea to help evaluate late stage field development scenarios and options. The Oseberg Formation consists of a sand-rich complex of Gilbert-type fan deltas situated along the western margin of the Hordaland platform on the eastern flank of the Viking Graben.

A non-linear evaluation using a neural network is tried on log data from 13 cored wells and extended to the remaining 23 uncored wells in the model area. Recognition of various sandy facies from well logs using the neural network is met with limited success. An extensive analysis of petrophysical data shows a better relationship between individual delta lobes than between similar facies in separate lobes. Facies analysis from cored wells also indicates that lateral facies transitions are abrupt and that only delta lobe boundaries, and not facies, can be correlated with certainty between wells.

A 3D model with grid size of 25x25x0.5m, and conditioned on well data, is generated for the Oseberg Formation using Irap-RMS6.0. Due to the uncertainty in facies distribution in uncored wells, rapid horizontal facies transitions and poor correlation between sedimentary facies and petrophysical parameters, 3D petrophysical models are generated directly for each delta lobe complex, thereby circumventing the need for a 3D facies model. Statistical transformations are applied to porosity and permeability data and variograms are defined with both the sedimentary model and grid dimensions in mind. Uncertainties in facies distribution are catered for in multiple realization scenarios by changing variogram dimensions. Results from modeling suggest that petrophysics is an excellent proxy for facies and that architectural elements of the Oseberg Gilbert deltas are readily identified in the 3-D petrophysical models.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado