General Geology of Lower Cretaceous Heavy Oil Accumulations in Western Canada
- L.W. Vigrass (Western Resources Consultants Ltd.)
- Document ID
- Petroleum Society of Canada
- Journal of Canadian Petroleum Technology
- Publication Date
- October 1965
- Document Type
- Journal Paper
- 168 - 176
- 1965. Petroleum Society of Canada
- 4.1.5 Processing Equipment, 4.3.4 Scale, 5.2 Reservoir Fluid Dynamics, 5.1.1 Exploration, Development, Structural Geology, 5.4.6 Thermal Methods, 5.7 Reserves Evaluation, 3 Production and Well Operations, 4.6 Natural Gas, 5.3.4 Integration of geomechanics in models, 5.4.10 Microbial Methods, 5.1.2 Faults and Fracture Characterisation, 1.10.1 Drill string components and drilling tools (tubulars, jars, subs, stabilisers, reamers, etc), 2.1.3 Sand/Solids Control, 1.2.3 Rock properties, 5.8.5 Oil Sand, Oil Shale, Bitumen
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Lower Cretaceous sand reservoirs contain about 750 billion barrels ofviscous, heavy oil along a broad arcuate belt that extends from northwesternAlberta into west-central Saskatchewan. The heavy oil is pooled in theMannville Group and, in a gross sense, occurs in a marine-continentaltransition facies. The accumulation at Peace River is in a regional onlapfeature. The accumulations in the Athabasca-Lloydminster region occur acrossthe crest and on the southwest flank of a regional anticlinal featureassociated with the solution of salt from Middle Devonian beds. These regionalfeatures had already formed by the end of Early Cretaceous time.
Chemical and physical properties of oils from different accumulations showthat they belong to a single oil system and suggest a common mode of origin.The Athabasca oil is young and immature and not evaporated, altered orpolymerized. The oil is not escaped and re-deposited Devonian oil. The mosttenable working hypothesis is that hydrocarbons moved out of sediments in thedeep basin in micellar solution in compaction waters. The hydrocarbons weredeposited as heavy asphaltic oil where physical-chemical conditions weresuitable. Early formed stratigraphic and structural "traps" served as loci ofdeposition for the heavy oil. Since deposition, and governed by buoyancy and capillarity, there has been some adjustment in position of the oil inthe traps.
This paper concerns the geology of the main belt of Lower Cretaceous heavyoil accumulations in Western Canada. It is hoped that the regional approachthat is used will improve our understanding of the individual accumulations andwill aid in their exploitation.
The main Lower Cretaceous heavy oil belt extends as a 600-mile arc fromPeace River in northwestern Alberta to Lloydminster in western Saskatchewan(Figure 1). The total amount of heavy oil reservoired in the sandstonesof the belt is immense, totalling at least 750 billion barrels of oil-in-place.About 95 percent of the known oil occurs in the Athabasca, Peace River, Wabascaand Cold Lake deposits.
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