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Lithology, reservoir properties, and burial history of portion of Gammon Shale ( Cretaceous), southwestern North Dakota.

American Association of Petroleum Geologists Bulletin

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Abstract

In the northern Great Plains, large quantities of biogenic methane are contained at shallow depths in Cretaceous marine mudstones. The Gammon Shale and equivalents of the Milk River Formation in Canada are typical. At Little Missouri field, Gammon reservoirs consist of discontinuous lenses and laminae of siltstone, enclosed by silty clay shale. Large amounts of allogenic clay, including highly expansible mixed-layer illite-smectite cause great water sensitivity and high water-saturation values. Studies show that the Gammon has not undergone thermal conditions sufficient for oil or thermal gas generation. The scarcity of authigenic silicates suggests that diagenesis has been inhibited by the presence of free methane. Shale layers are practically impermeable whereas siltstone microlenses are porous (30-40%) and have permeabilities on the order of 3-30 md. Organic matter in the low-permeability reservoirs served as the source of biogenic methane, and capillary forces acted as the trapping mechanism for gas accumulation. Much of the Gammon interval is potentially economic. -from Author

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Lithology, reservoir properties, and burial history of portion of Gammon Shale ( Cretaceous), southwestern North Dakota.
Series title:
American Association of Petroleum Geologists Bulletin
Volume
65
Issue:
6
Year Published:
1981
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
First page:
1146
Last page:
1159
Number of Pages:
14