--> Abstract: Reservoir Description of the Crossfield Member of the Wabamun Group, Western Canada, Using Core Description, Geostatistics, and Pressure Buildup Tests, by L. B. McNamara and N. C. Wardlaw; #91012 (1992).

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ABSTRACT: Reservoir Description of the Crossfield Member of the Wabamun Group, Western Canada, Using Core Description, Geostatistics, and Pressure Buildup Tests

MCNAMARA, L. B., and N. C. WARDLAW, The University of Calgary, Calgary, Alberta, Canada

The gas-producing Crossfield reservoir unit within the Upper Devonian Wabamun Group provides an excellent example for understanding the role of geological, geostatistical, and production data in the estimation of average permeability. The Crossfield carbonates were deposited on a low energy, shallow water carbonate shelf. The shallowing upward sedimentary cycles include the following: subtidal unfossiliferous muds, shallow subtidal mudstones to packstones with stromatoporoids or gastropods, intertidal sediments containing gastropods and fenestral fabrics, and laminated supratidal sediments. Anhydrite occurs as replacement of original gypsum, as displacive nodules and as a pore-filling cement.

The unfossiliferous muds and laminated supratidal sediments are nonproductive. The stomatoporoid or gastropod-dominated shallow subtidal sediments have the best reservoir properties, but reservoir quality depends upon the amount of original fossil material present, the degree to which moldic and vugular porosity have been created, and the amount of void-filling anhydrite that occludes porosity. Intertidal sediments containing fenestral pores and gastropod molds are also of good reservoir quality. Individual wells producing from similar facies can have a wide range of production rates.

Incorporation of geologic information in the reservoir description permits the following: association of reservoir facies with the petrophysical and production characteristics essential for mapping reservoir quality; assignment of a probability distribution for permeability to productive and nonproductive reservoir facies; recognition of a high bias in the core analysis that must be taken into account when estimating average permeability. All of these are necessary for prediction of reservoir quality in unsampled regions of reservoirs.

 

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)