Chad R. Harris1, Murray K. Gingras2, S. George Pemberton1
(1) University of Alberta, Edmonton, AB
(2) University of New Brunswick, Fredricton, NB
ABSTRACT: Ichnofossil Evidence from the Estuarine Facies of the McMurray Formation, northeast Alberta: Facies Interpretation and Possible Production Enhancement
Northeast Alberta plays host to extensive heavy oil and bitumen deposits the largest of which, the Athabasca Oil Sands, contains approximately 1.3 trillion barrels of bitumen in-place, trapped in the non-lithified, surface-exposed, sand of the McMurray Formation. Given the size of this resource and its proven recoverability, this deposit is unquestionably the future of the oil industry in western Canada. Comprehension of the geology of this deposit and effective production techniques will ensure the longevity of this industry in Alberta. Ichnological criteria have long been key to understanding the inherent and complex mosaic of these fluvial to shallow marine facies. These ichnofossils may now have an impact on in-situ production.
The traditional fossil data in the McMurray Formation is rare and limited to marine bivalves and common wood fragments. Ichnofossils are readily recognizable in the rock record and their interpretation allows for better understanding of the palaeo-environments of distinct facies through several factors. Many ichnofossils have been identified in the McMurray Formation, notably Skolithos, Cylindrichnus, Gyrolithes, Conichnus, Monocraterion, Planolites, and Palaeophycus.
Steam Assisted Gravity Drainage (SAGD) in-situ techniques are undoubtedly the future of the oil sands industry. This production method requires good vertical continuity in the defined pay zones of the deposit. Commonly these zones comprise the inclined beds known as Inclined Heterolithic Stratification that contain alternating beds of sand and steam impeding mud of variable thickness. The sand-filled vertical burrows Skolithos, Cylindrichnus, and others penetrate the mudstones and generate vertical permeability through these beds. They therefore penetrate possible steam seals and can enhance SAGD production techniques.
AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado