ABSTRACT

Geochemical analyses have been conducted on thirty-six crude oil and condensate samples from the Scotian Shelf. These families of crude oils and condensates have been defined on the basis of n-alkane distributions, pristane-to-phytane ratios, carbon isotope distributions in the saturate and aromatic fractions, distributions of twenty-six gasoline-range hydrocarbons and ring distributions in the aromatic fraction. Biodegraded samples occur in the upper part of the Logan Canyon Formation and the Wyandot Formation. The three families of crude oils are largely confined to discrete stratigraphic units within which they are thought to have been generated. These units are: 1) Wyandot Formation, 2) Logan Canyon Formation, 3) Mic Mac, Missisauga and Verrill Canyon Formations. The occurrence of separate families of oils at relatively shallow depths provides additional evidence for the local maturation and generation of hydrocarbons in sediments at local thermal anomalies which may or may not be associated with salt diapirism. Except in the Wyandot samples, the pristane-to-phytane ratios indicate that the oils and conde ates were derived at least in part from terrestrial organic matter.