Seismic Geomorphology of Tidally Influenced Fluvial Deposits in the McMurray Formation, Canada: Overview of Depositional Elements
Bitumen of the Lower Cretaceous McMurray Formation in Alberta arguably represents one of the most important hydrocarbon accumulations in the world. In-situ development of the deposit is largely accomplished through steam assisted gravity drainage (SAGD), a process whereby horizontal steam injection wells are placed < 6 m above horizontal producers near the base of the sandstone reservoir. Given this technology, understanding the distribution of the resource is paramount for a successful development program. Sedimentary facies provide a direct control on bitumen distribution and recovery.
Most facies models developed to describe and predict sedimentary units of the McMurray Formation consider fluvial, estuarine and/or deltaic depositional settings. SAGD development, however, requires a particularly high-resolution sedimentological interpretation. High-quality three-dimensional seismic reflection data and extensive drill cores from acreage located approximately 50 km south of Fort McMurray provide important insight into the sedimentological organization of reservoir and non-reservoir deposits in the upper third (40 m) of the reservoir interval. Geomorphologic characteristics of the strata observed in seismic time slices reveal a fluvial depositional setting was prevalent. Ichnologic and palynologic data, as well as sedimentary structures suggestive of tidal processes, indicate a slight marine influence in the upper reaches of a fluvial system characterized by channels 400-700 m wide and 30-40 m deep. The complicated stratigraphy imaged seismically consists of a mosaic of large-scale depositional elements including point bars that evolved through lateral channel migration, point bars developed through downstream translation, counter point-bars (> 50% silt), sandstone-filled channels, and abandoned channels or oxbows. Reservoir deposits are primarily associated with point bars and sandstone-filled channels.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009