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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 42 (1958)

Issue: 1. (January)

First Page: 211

Last Page: 211

Title: Facies Patterns and Oil Accumulation in Pennsylvanian of Southern Oklahoma: ABSTRACT

Author(s): E. C. Dapples, L. L. Sloss

Article Type: Meeting abstract


Analysis of the complex facies patterns expressed by Pennsylvanian strata of southern Oklahoma requires identification of regionally extensive, correlatable, stratigraphic units. The writers have been able to extend a correlation network based on recognition of cyclical units which can be grouped into major operational mapping units separated by regional unconformities. The resulting stratigraphic subdivisions, both major and minor, are not those of the formal stratigraphic nomenclature accepted in the area but they do make possible a classification of trapping conditions related to position in the stratigraphic succession. The types are as follows: (1) blanket sands in which facies trapping components are markedly subordinate to structure; (2) discontinuous sand bodies w th traps largely independent of structural axes; differentiation can be made between major sand bodies of greater areal extent than the associated structures, and minor sand bodies significantly smaller than the areas of the structures on which they lie; (3) traps related to unconformities, including channel fills, overlapping strand-line sands associated with marine transgression across major structures, truncation traps sealed by overlying permeability barriers, and secondary accumulations in permeable strata overlying truncated reservoirs; (4) sandstone reservoirs with apparent random distribution and without discernible relationships to facies patterns.

Relationships of the trap types enumerated can be demonstrated in terms of position in the stratigraphic succession, time and geography of structural growth, development and character of major unconformities, and other elements of the regional geologic history.

The regional study raises a number of questions which are not easily resolved but certain tentative conclusions can be drawn from analysis of regional and local facies patterns. Such questions include: (1) vertical homogeneity of areas either rich or poor in number and thickness of sand bodies; (2) relationship of limestone conglomerate to reservoir and sealing components; (3) diagenetic introduction of carbonate cement in relationship to time of oil accumulation; (4) volumetric proportions of sand and marine shale requisite to significant oil accumulation.

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Copyright 1997 American Association of Petroleum Geologists