Nunavut Stratigraphy/Energy (2007)

S. Zhang (CNGO)

The Nunavut Stratigraphy/Energy project is intended to re-evaluate the hydrocarbon potential of selected regions in Nunavut by providing new data and ideas on some of the known and under-explored regions in the territory.

Hudson Bay Biostratigraphy: Evaluating Thermal Maturation of Lower Paleozoic Stratigraphy and implications for hydrocarbon generation.

The Hudson Bay basin is one of the largest Paleozoic sedimentary basins in North America. It was explored, in a very preliminary way, more than 30 years ago, although the hydrocarbon potential remains largely untested. To evaluate the thermal maturation of the lower Paleozoic rocks, conodonts were examined from rocks sampled by six exploration wells in the on-shore and off-shore parts of the basin. The study included almost 4500 conodonts from 390 conodont-bearing samples taken from continuous cores and well cuttings. The work has revealed approximately 50 species representing 28 genera. The conodont studies have significantly improved our understanding of the basin by providing:

1. A clear definition of conodont zones and their stratigraphic ranges.
2. Precise biostratigraphic control for the different formations resulting in better correlation between exploration wells.
3. Recognition of sea-level events based on the stratigraphic distribution and known ecologic partitioning of key conodont species.

Conodonts from the six wells studied have a Colour Alteration Index (CAI) value of 1, indicating little alteration of organic matter and that the strata have not reached burial temperatures greater than 80 C. On this basis, the Late Ordovician and Early Silurian strata intersected in the wells are interpreted to have not reached the lowest temperature (~ 100 C) required for hydrocarbon generation. Of significance, the Boas River oil shale, a potential source rock, which occurs at surface on Southampton Island, does not appear to be represented in the off-shore wells.

In addition to the conodont studies, 241 samples were collected from the wells and submitted for Rock Eval Pyrolysis testing. The data will quantitatively analyze the thermal maturation of Paleozoic rocks in order to assess the potential for hydrocarbon generation in Hudson Bay and Foxe basins.