Shell Canada has obtained geochemical data on samples from 56 of the 67 wells drilled to January, 1978, on the Nova Scotia Shelf. This paper discusses the use of these data, combined with other data, in evaluation of the oil and gas potential of the shelf.

Interpretation includes source rock identification, regional maturity considerations, oil classifications, hydrocarbon shows, and migration aspects. For a source rock to be capable of expelling oil and gas, minimum values in three parameters are required, organic richness, organic type, and maturity. By this definition well-developed source rocks have not been penetrated. Only the very deep tests reach rocks of sufficient maturity for oil and gas expulsion. Potential source rocks are indicated by scattered occurrences of thin, organic-rich, lipid and humic laminae, the best of which are in the Verrill Canyon Formation of the Sable Basin, and the Iroquois Formation of the Abenaki Basin. Chemical analyses of 22 oils and condensates from seven wells characterize the oils into two typing groups, one from each basin, supporting the presence of only two source rocks or types of source rocks. Hydrocarbon shows determined from mud logs, oil staining fluorescence, as well as actual accumulations, are almost entirely confined to the two basins. This distribution of shows is interpreted to result from localized source rock development, and the existence of vertical communication from deep source rocks to shallow reservoirs, primarily by means of piercement-associated faulting.

Based on presently available geochemistry data, interpretation suggests that the best exploration potential for the Nova Scotia Shelf is in the Abenaki and Sable Basins, where accumulations have already been found.