Modelling a mature and depleted fluvial reservoir, with relatively thin sand crops difficult to locate on the seismic, inflicts very large uncertainties in the simulation model compared to models of more traditional shallow marine systems. Previous models have failed, and thus a different approach has been made for modelling and history matching the fluvial reservoir. To better capture all available data, especially dynamical data, a new modelling process has been developed. This modelling process involves three vital stages: the Data Handling Stage, the Conceptual Stage and the Modelling Stage. All three stages require a large degree of intradisciplinary work. Combining the work process with advanced software and geostatistical techniques, a total modelling package designed to capture large quantities of data has been developed.
The modelling process has been applied on the fluvial Upper Ness Formation located on the Alpha North structural segment of the Oseberg Field. The highly iterative process has proven successful on this strongly heterolithic and poorly understood reservoir. As a consequence, future development plans of the area have been changed, and two new production well targets are located. Planning of the targets in detail has begun and the first well will be drilled during the autumn of 2005.
The Oseberg Field is located on a large-scale tilted fault block in the Horda Platform area of the Norwegian North Sea sector (Figure 1). The dominant part of the production from this field comes from the Middle Jurassic deltaic deposits of the Brent Group (Figure 3) (Spencer and Larsen, 1990), which represents a regressive/transgressive, large scale, cycle of sedimentation, where the Ness Formation constitute the upper delta plain depositional unit (Enyon, 1981; Graue et al., 1987, Helland-Hansen et al., 1992; Johannesen et al., 1995; Ryseth, 2000). The fluvial Ness Formation has contributed to the total oil production of the North Sea Oseberg Field since production commenced in 1988.