Characterization of Mississippian Osage Chat in South-Central Kansas

Kansas Geological Survey
Open-file Report 2002-50

Rock Petrophysics

Lithofacies and Petrofacies

Spivey-Grabs Field
Core and Petrophysical Analysis of Miss. “Chat”
General Atlantic Tjaden #A-1 WIW #1
ne sw sw Section 24, T30S, R8W
Kingman County, Kansas

While the Mississippian chat reservoirs of south-central Kansas reflect a specific depositional and diagenetic history, the lithofacies present, the nature of chert formation and dissolution and fracturing, and the log and core petrophysical properties are likely to be representative of other shallow shelf chert systems or may shed light on controls in these systems. The most productive and economic chat reservoir is a tripolitic chert exhibiting variable degrees of sponge spicule mold content, chert microporosity, dissolution vuggy porosity, autoclastic brecciation, and clay infill of fractures.

A core described below from the General Atlantic Tjaden 1-A WIW contains a succession of four stacked shallowing-upward cycles in which a complete cycle comprises beds dominated by the following lithofacies from bottom to top: 1) argillaceous dolomite mudstone; 2) argillaceous dolomite mudstone with chert nodules; 3) clean dolomite mudstone with nodular chert; 4) nodular to bedded chert; 5) autoclastic chert; 6) autoclastic chert with clay infill; and 7) bioclastic crinoidal wackestone to grainstone.

Lithofacies of Chat reservoirs in south-central Kansas.

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Last updated January 2003