THE USE OF OIL FINGERPRINTING TO ENHANCE FIELD PRODUCTION ON BARROW ISLAND

Abstract

Oil production from well B28 completed in the Windalia Sand Reservoir of the Barrow Island Field was anomalously high in comparison to surrounding wells. Reservoir properties evaluated from the well could not account for the high production rates. Oil fingerprinting, which is a reservoir-geochemistry technique based on the gas chromatographic character of oil, was applied to identify the reservoir affiliation of the additional oil. The oil fingerprinting indicated that the oil from the B28 well is geochemically similar to oil from the deeper Flacourt Formation Reservoir.

The results of the oil fingerprinting prompted a re-evaluation of the existing geological model in the area of well B28. The well intersects the Barrow Fault within a downthrown sliver of Windalia Sand. A large volume fracture stimulation over this interval may have opened the Barrow Fault to the underlying upper Flacourt Formation Reservoir. However, the structure outlined by the oil-water contact in the upper Flacourt Formation Reservoir had been mapped as a four-way dip closure 500 m north east of the B28 well. A review of the local stratigraphy identified a thin sand (the B28 sand), at the top of the Lowendal member of the IYluderong Shale, which could form a conduit from the Barrow Fault to the nearby upper Flacourt Formation Reservoir. The interpretation of the B28 sand conduit also increased the mapped extent of the upper Flacourt accumulation. In December 1997, 41 years after development began on Barrow Island, the B28 sand was successfully targeted by infill well CUM and subsequently developed as an extension to the Flacourt accumulation. Well CUM has the second highest initial production rate (1,360 BOPD) in the history of the field. The application of oil fingerprinting has enhanced the stratigraphic and structural model of an area with limited well control and sparse, poor quality seismic.