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A multidisciplinary analysis of Belly River-Brazeau (Campanian) fluvial channel reservoirs in west-central Alberta, Canada

Peter E. Putnam
A multidisciplinary analysis of Belly River-Brazeau (Campanian) fluvial channel reservoirs in west-central Alberta, Canada
Bulletin of Canadian Petroleum Geology (June 1993) 41 (2): 186-217

Abstract

An integrated surface and subsurface study, encompassing reservoir geometry, petrography, hydrodynamics and seismic, of the lower 200 metres of the Campanian Belly River Formation in west-central Alberta suggests the presence of a regional "deep basin" style of oil accumulation. In this setting hydrocarbons are found in the deepest (western) portions of the basin downdip of aquifers within lenticular fluvial reservoirs with northeasterly paleocurrent orientations which traverse a western northwest-striking fold and fault belt and an eastern northeast-striking fracture network. Faulted channel fills form traps in the western portions of the basin whereas updip sandstone pinchouts localize hydrocarbons in the shallower regions found in the east. The bulk of the lower Belly River Formation is interpreted to have been deposited within anastomosed fluvial environments. The interpreted paleogeographic setting and reservoir geometries of this fluvial system are compatible with the map views of the major channel fills, the mud-rich nature of the unit, the degree of hydrodynamic communication within channel fill trends, the nature and distribution of porosity and the seismic responses of channel fills. The major reservoir units are channel fills with thicknesses of 20 to 30 metres, widths up to several hundred metres and individual segments can be mapped over several tens of kilometres. Flanking rocks comprise rippled sheet sandstones interbedded with coaly mudstones; the latter are volumetrically the most significant deposits within the interval studied. The Belly River Formation displays progressive underpressuring in a westerly direction which reflects, in part, postorogenic erosion. The westernmost underpressured portions of the study area coincide with a potentiometric low within which hydrocarbons are the dominant interstitial fluid. To the east and updip localized oil pools with attendant aquifers are encountered. Individual channel fill segments display pressure communication over tens of kilometres. These conditions of hydrocarbon accumulation appear to cover several thousand square kilometres oriented along depositional and structural strike. In the western disturbed belt primary porosity is preserved within grain-supported conglomerates and pebbly sandstones associated with channel fills located in positions proximal to source terranes. Further east, secondary porosity predominates in sandy chert litharenite lithofacies and the best developed porosity is found adjacent to fractures which enhanced fluid migration and grain dissolution. Prior petroleum industry emphasis on deeper targets in this portion of western Canada has inhibited seismic delineation of Belly River reservoirs. The thickest reservoir bodies (20 metres and greater) and major structures (i.e., those with relief of 30 to 50 metres) are seismically resolvable if acquisition parameters are employed which utilize small group intervals and emphasize near trace data. Analysis of established productive trends reveals many criteria applicable to further exploration and more efficient exploitation. A case study is presented which illustrates the application of the concepts forwarded here to defining successful new drilling locations and new prospective areas are proposed. It is conceivable that new fields with over 14.7 million m3 (100 million barrels) of oil-in-place await discovery in the deeper parts of the basin whereas smaller accumulations with 2.9 to 3.7 million m3 (20-25 million barrels) of oil-in-place will be discovered in the shallower, eastern portions of the area examined.


ISSN: 0007-4802
Coden: BCPGAI
Serial Title: Bulletin of Canadian Petroleum Geology
Serial Volume: 41
Serial Issue: 2
Title: A multidisciplinary analysis of Belly River-Brazeau (Campanian) fluvial channel reservoirs in west-central Alberta, Canada
Author(s): Putnam, Peter E.
Affiliation: Petrel Robertson, Calgary, AB, Canada
Pages: 186-217
Published: 199306
Text Language: English
Summary Language: French
Publisher: Canadian Society of Petroleum Geologists, Calgary, AB, Canada
References: 56
Accession Number: 1993-019747
Categories: Economic geology, geology of energy sourcesSedimentary petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. block diag., sects., strat. cols., sketch maps
N49°00'00" - N60°00'00", W120°00'00" - W110°00'00"
Country of Publication: Canada
Secondary Affiliation: GeoRef, Copyright 2020, American Geosciences Institute.
Update Code: 1993
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