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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


DOI: 10.1306/02191615118

Porosity and pore size distribution in mudrocks from the Belle Fourche and Second White Specks Formations in Alberta, Canada

Agnieszka Furmann,1 Maria Mastalerz,2 David Bish,3 Arndt Schimmelmann,4 and Per Kent Pedersen5

1Department of Geological Sciences, Indiana University, 1001 East 10th Street, Bloomington, Indiana 47405; present address: Schlumberger, 1935 South Fremont Drive, Salt Lake City, Utah 84104; [email protected]
2Indiana Geological Survey, Indiana University, 611 North Walnut Grove Avenue, Bloomington, Indiana 47405; [email protected]
3Department of Geological Sciences, Indiana University, 1001 East 10th Street, Bloomington, Indiana 47405; [email protected]
4Department of Geological Sciences, Indiana University, 1001 East 10th Street, Bloomington, Indiana 47405; [email protected]
5Department of Geoscience, University of Calgary, 2500 University Drive Northwest, Calgary, Alberta T2N 1N4, Canada; [email protected]


The distribution of porosity was examined on seven drill cores from west–central Alberta encompassing the Belle Fourche and Second White Specks Formations. These Cenomanian–Turonian mudrocks from the Western Canada Sedimentary Basin exhibit good organic richness (>2 wt. % total organic carbon) and marine kerogen type II with limited kerogen type III. With the increasing thermal maturity from approximately 0.43% vitrinite reflectance (Ro) to approximately 0.90% Ro, the total porosity decreases from approximately 9 to approximately 1 vol. %. This change translates to a reduction in total pore volume from approximately 0.05 to approximately 0.005 cm3/g and is accompanied by changes in relative proportions of micropore, mesopore, and macropore volumes. Variations in total porosity for the seven cores with different thermal maturities across Alberta are mainly related to mesoporosity and macroporosity, although the in-core variations in total porosity are mainly related to microporosity. In general, organic matter micropores contribute to the overall microporosity in the seven cores across the study area. The increase in the total pore volumes is in accordance with an increasing concentration of quartz, although increasing concentrations of chlorite and kaolinite may contribute to greater abundance of micropores in the seven cores. The in-core variations suggest that greater contents of kaolinite and illite may contribute to increasing mesopore volumes. Variations in pore volumes and pore size distribution with depth within individual cores (representing specific thermal maturity level) differ from what is observed laterally, when cores of various thermal maturity levels across Alberta are compared, indicating complex controls on porosity systems.

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