Petrophysical Well Log Attributes of the Late Devonian Duvernay Shale in Alberta, Canada

The Duvernay Shale is an upper Devonian interval of organic-rich laminated, dark, bituminous, thermally mature mud rocks and carbonates that are interbedded with gray-green calcareous shales. The Duvernay is currently an active unconventional exploration target within Alberta, Canada. This study compares standard well-log data with observed depositional facies in order to identify indicators of organic richness and reservoir quality potential within the East Shale Basin. Data from the East Shale Basin is compared to its liquid rich, and highly productive counterpart, the West Shale Basin. Data maps were constructed through the analysis of more than 400 vertical well-logs through the Duvernay across the study area. Five data parameters (interval thickness, gamma radiation, photoelectric effect, estimated source rock proportion, and estimated source rock thicknesses) were collected and recorded from these logs. The Duvernay is thinnest, and most organic-rich within the West Shale Basin, and is characterized by the highest overall gamma radiation and photoelectric cross section (PE) values suggestive of a dominantly siliciclastic mineralogic composition. Conversely, the East Shale Basin is thicker, has lower organic richness, and PE values suggestive of a calcite mineralogic composition. These attributes, combined with the broader range of favorable thermal maturity within the West Shale Basin, suggest that the greatest hydrocarbon exploration potential occurs within the West Shale Basin.