A Sr Residual Salt Analysis (SrRSA) Study to Investigate the Connectivity of the Brent Group Reservoir of the Dunbar Field, UK North Sea: ABSTRACT

Abstract

The Middle Jurassic Brent Group reservoir sequence of the Dunbar oilfield in the UK Northern North Sea consists of interbedded fluvio-deltaic sandstones, mudstones and coals. This sequence occurs within rotated fault block structures on the western margin of the North Viking Graben. Strontium Residual Salt Analysis (SrRSA) has been performed on 254 core samples from 9 wells in the Dunbar Field. SrRSA data are {sup 87}Sr/{sup 86}Sr ratios from residual salts (and/or water) extracted from reservoir cores. These data reflect the {sup 87}Sr/{sup 86}Sr ratios of irreducible waters at the time they were trapped by hydrocarbons. Profiles of variation of SrRSA {sup 87}Sr/{sup 86}Sr ratios with depth were integrated with sedimentological, structural and petrophysical data to assess compartmentalization within and between the study wells. The results of this study suggest that certain coal and mudstone beds are laterally extensive scaling barriers which isolate flow units within the Brent reservoir. In addition, these data have also indicated that other barriers - which may be seated faults are present between certain wells in the field area. The results of this study have confirmed some aspects of the pre-existing reservoir model and thus enhanced confidence in the interpretations. The SrRSA data have alsomore » highlighted previously unexpected aspects of reservoir connectivity and thus enabled informed decisions to be made on the optimum production strategy. The integration of SrRSA with the geological and reservoir engineering database during the development phase may thus have helped optimize production from the Brent reservoir of the Dunbar Field.« less