REBEC, TONY, Halliburton Geophysical Services, Inc., Fulshear, TX

ABSTRACT: Reservoir Monitoring Using Seismic Methods, Part 2 -- Case History

A monitoring pilot study over Norsk Hydro's Oseberg field was conducted to confirm that monitoring hydrocarbon fluid movement in this producing reservoir was possible using repeat 3-D seismic data.

Two 3-D surveys were collected about 16 months apart using the same vessel and equipment, and processed using identical parameters. It was important to maneuver the monitor survey in 3-D space to the base survey to allow for an optimum comparison. A detailed interpretation of both, which included intra-Brent events, was made, and the high similarity between interpretations noted. The stratigraphic parameters were used to build an acoustic model of the reservoir, which was refined by seismic inversion methods such that the refined geologic model best fitted both the initial geologic model and the seismic data. The refined model was reservoir simulated to estimate fluid saturations corresponding to the dates of the two seismic surveys, and these saturations used for comparison with the bserved seismic differences.

The comparison showed a seismic anomaly between the two 3-D surveys at a position where the gas-oil contact was expected to move. This had the spatial continuity and extent of a similar shape in the simulated saturation changes. The seismic data provided evidence of the configurations of fluid fronts between wells that was not directly observable from well data.

AAPG Search and Discovery Article #90994©1993 AAPG Southwest Section Meeting, Fort Worth, Texas, February 21-23, 1993.