Control on reservoir distribution and quality in regressive member of an Upper Pennsylvanian cyclothem
Isopach maps and diagenetic features may be used to predict the distribution of reservoir-quality rock in the D-zone cyclothem of the Lansing-Kansas City Groups in southwestern Nebraska. The D-zone cyclothem was deposited during one major oscillation of the epeiric sea in late Pennsylvanian (Missourian). This cyclothem records a transgression of sea level followed by a major regression. During the regressive phase there was a brief sea level transgression. The D-zone cyclothem consists of the four basic lithofacies common to most cyclic deposits of this age in northwestern Kansas and southwestern Nebraska: 1) a thin lower carbonate unit deposited in a shallow-marine environment; 2) a laterally extensive lower shale unit of marine origin resulting from a terrigenous influx from the north; 3) a complex upper carbonate unit deposited in shoaling water during waning terrigenous influx; and 4) an upper shale unit deposited in tidal flat to nonmarine environments. Conclusions: 1) paleobathymetery is reflected in an isopach map of the upper shale unit; 2) distribution of grain-supported rock is controlled in part by formation of bathymetric highs while underlying shales compacted around preexisting topographic highs; 3) enhancement of porosity by dissolution in the grain-supported rocks occurred in the freshwater phreatic and vadose zoes; and 4) recognition of diagenetic features associated with formation of paleowater tables may be used to predict the distribution of porosity in these grainstones.
- Research Organization:
- Shell Oil Co., New Orleans, LA
- OSTI ID:
- 6527159
- Report Number(s):
- CONF-8310309-
- Journal Information:
- Am. Assoc. Pet. Geol., Bull.; (United States), Vol. 67:8; Conference: AAPG Mid-Continent Section meeting, Wichita, KS, USA, 16 Oct 1983
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
03 NATURAL GAS
NEBRASKA
RESERVOIR ROCK
DISTRIBUTION
POROSITY
STRATIGRAPHY
DIAGENESIS
DISSOLUTION
LITHOLOGY
PENNSYLVANIAN PERIOD
SEDIMENTATION
FEDERAL REGION VII
GEOLOGIC AGES
GEOLOGY
NORTH AMERICA
PALEOZOIC ERA
USA
020200* - Petroleum- Reserves
Geology
& Exploration
030200 - Natural Gas- Reserves
Geology
& Exploration