Ma. Mccaffrey et al., SOURCE-ROCK QUALITY DETERMINATION FROM OIL BIOMARKERS .2. A CASE-STUDY USING TERTIARY-RESERVOIRED BEAUFORT SEA OILS, AAPG bulletin, 78(10), 1994, pp. 1527-1540
Biomarkers (molecular fossils) in 26 Beaufort Sea Mackenzie delta oils
reveal three genetic oil groups and suggest descriptions of their pro
bable sources. Group 1 (21 Tertiary-reservoired oils) was sourced from
Tertiary deltaic sediments. Group 2 (three Cretaceous- and one Devoni
an-reservoired oil) and group 3 (one Lower Cretaceous-reservoired oil)
derive from two high-quality sources deposited in open-marine environ
ments. Geographical variations in the geochemistry of the 21 group 1 o
ils suggest that their deltaic source was substantially more oil-prone
in the distal deltaic portions than in tile region closer to the pale
oshoreline. Although these data do not address source rock volumes, th
ey do indicate that poor source quality is not a cause of underfilled
traps in the offshore. The mappable lateral variations in group 1 oil
compositions illustrate how, in basins with vertically drained sources
, lateral source rock facies changes can be inferred from regional var
iations in the geochemistry of the overlying oils. Furthermore, the da
ta suggest that geochemical studies attempting to deduce genetic relat
ionships between geographically separated oils should carefully consid
er the potential effects of source rock facies changes on the oil comp
ositions.