Fracture Characterization of Giant Heavy Oil Accumulation in Carbonates, Northeast Alberta, Canada

The Grosmont Carbonate Platform, located in northeastern Alberta, Canada, holds one of the largest accumulations of hydrocarbons in the world. The resource is a heavy oil accumulation, hosted in porous, fractured and karsted carbonates. Shell’s leases in the Grosmont represent a significant share of this resource base. However, development of this heavy oil accumulation is challenging from the perspective of reservoir characterization. Fracture and karst description are key to predicting the performance of this giant hydrocarbon resource.

The carbonates are fractured at a variety of scales. Fractures and karst, which are potential fluid conduits in the reservoir, are saturated with bitumen, which will be mobilized during the development process. They also provide potential conduits to introduce steam into the reservoir, one possible recovery method. This study shows that fractures and karst are often coupled processes and that fractures are not only tectonic in origin but also related to collapse, compaction, and diagenetic processes. We show evidence of the various origins of fracturing and the characterization of their geometry, connectivity, relationships with the stratigraphy, and relative timing. We show how the use of legacy interpretations, careful description of cores, outcrop data and the integration with detailed stratigraphic and diagenetic data help Shell focus on critical G&G aspects of the reservoir. The study also shows the role and importance of rock calibration and outcrop information for a holistic understanding of the reservoir geology and illustrates the challenges of trying to reconcile data and interpretations that come from advanced technologies and more standard methods.
 

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California