Lowstand/Transgressive Upper Cretaceous (Coniacian) Gravelly Deltaic Complexes of the Cardium Formation, West Central Alberta, Canada

David V. Thomas

A detailed facies and sequence stratigraphic analysis is used to demonstrate the reservoir compartmentalization of gravelly deltaic complexes deposited on a ramp margin in the Western Canadian Sedimentary Basin. Gravelly deltas of the Carrot Creek Member of the Cardium Formation in the Cyn Pem Field area of West Central Alberta occur along well defined backstepping shoreline trends that represent high frequency lowstand to transgressive systems tracts that followed the second order sea level fall (~90 Ma) of the Turonian.

The Cyn Pem Cardium D pool is used to illustrate the detailed sedimentology and stratigraphy of a gravelly deltaic complex. The pool consists of two distinct coarse-grained delta lobes oriented along a northwest- trending shoreline. Up to 21 metres of gravelly stream mouth bar and distributary channel facies were deposited unconformably on distal marine highstand deposits of the Raven River Member (Turonian) of the Cardium Formation. Production data and facies analysis indicates excellent communication along high permeability (>1 Darcy) Gilbert-type deltaic foresets oriented parallel to strike and moderate to poor communication in a depositional dip direction. Poorly sorted gravelly distributary channels dissect the deltaic foresets.

A complex history of high frequency lowstand and transgressive erosion resulted in substantial paleotopographic relief that both bounds and compartmentalizes these gravelly deltaic complexes.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California