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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 66 (1982)

Issue: 10. (October)

First Page: 1705

Last Page: 1706

Title: Computer Modeling of Minnelusa Formation (Pennsylvanian-Permian) Paleotopography in Eastern Powder River Basin, Wyoming: ABSTRACT

Author(s): R. Mark Maslyn

Article Type: Meeting abstract

Abstract:

The great majority of Minnelusa Formation (Pennsylvanian-Permian) oil production in the eastern Powder River basin is derived from various types of stratigraphic traps which resulted from paleotopographic relief developed on the upper Minnelusa. This relief is mirrored by thickness variations in the overlying Opeche Shale (Permian). Construction of isopachous maps of the Opeche is one of the methods used to explore for paleotopographic traps in the Minnelusa.

Hand-contoured Opeche isopachous maps may be subject to ambiguous interpretations in areas where the data points are scattered or nonexistent. This difficulty is partially overcome when the isopachous map is produced by mathematical methods.

The upper Minnelusa paleotopography is believed by the author to reflect eolian sand dunes encased by the red shale of the Opeche. Observations from oil tests in the area indicates

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that this paleotopography has a cyclicity, with a crest wavelength of approximately 3 mi (5 km). Double Previous HitFourierNext Hit transforms are most appropriately used in modeling where such a cyclicity exists.

The resulting double Previous HitFourierTop transform-generated computer model of the upper Minnelusa paleotopography shows a good correlation between the observed data points and the calculated best-fit surface. Additionally, the computer generated surface suggests areas away from present production and drilling which may warrant further exploration.

The computer generated surface data must, however, be integrated with other known geologic data and examined closely in areas where the control point spacing exceeds either the x or y direction fundamental wavelengths.

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