RESERVOIR OVERPRINTING OF CRUDE OILS

Biomarker concentrations are generally low in high API gravity oils an d condensates. Admixture of even small amounts of low-maturity, biomar ker-rich bitumen can drastically alter the biomarker profile of such f luids. We suggest that a 41 degrees API DST oil from the Sunfish #1 we ll, Cook Inlet, Alaska, is a mixture of Jurassic-derived oil with appr oximately 5 wt% Tertiary input derived from coals interbedded with the reservoir sands. Reservoir overprinting has significantly altered the biomarker fingerprint of the Sunfish #1 oil. Therefore, biomarker pat terns or parameters for biomarker-lean, high API gravity fluids should be scrutinized closely for internal consistency and conformity with b ulk properties.