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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 63 (1979)

Issue: 5. (May)

First Page: 832

Last Page: 833

Title: Influence of Diagenetic Reactions on Nonmarine Upper Cretaceous Rocks of Southman Canyon Gas Field, Uinta Basin, Utah: ABSTRACT

Author(s): C. William Keighin, Thomas D. Fouch

Article Type: Meeting abstract

Abstract:

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Natural gas is produced from sandstone in the Upper Cretaceous Neslen, Farrer, and Tuscher Formations in the southeastern Uinta basin. Examination of these sandstone units along the eastern Book Cliffs indicates that most of the reservoir units are part of alluvial channels. Sandstone beds in the Neslen represent relatively small and isolated meandering channels in swampy coastal plains. Sandstone beds in the Farrer were deposited by somewhat larger and more numerous meandering streams depositionally upslope from the Neslen setting. The Tuscher Formation represents the most landward facies and was deposited principally by meandering, laterally migrating, large streams with local braided courses.

Core samples from the Southman Canyon gas field studied with the scanning electron microscope (SEM) indicate that extensive diagenetic modifications of the reservoir rocks have occurred and have strongly influenced reservoir characteristics.

Authigenic overgrowths on detrital quartz are common, but secondary silica is not a significant cementing agent. Feldspars are not abundant and are commonly altered to illitic clay. Carbonate minerals--dolomite, ankerite, calcite, and minor siderite--account for up to 20% of the rock. They are generally interstitial and have replaced some detrital quartz and rock fragments. Chert and other rock fragments account for more than 20% of the volume of many sandstones. Some rock fragments are extensively altered by mechanical deformation, dissolution, and clay-mineral formation. Dissolution and leaching, primarily of rock fragments, have improved the reservoir storage capacity of the sandstone units by producing a significant amount of intergranular and intragranular secondary porosity. The dissolution and leaching appear to have exerted a greater influence on reservoir characteristics than did mechanical deformation and growth of authigenic minerals. Most porosity in the units is of secondary origin.

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