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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 57 (1973)

Issue: 9. (September)

First Page: 1821

Last Page: 1821

Title: Porosity and Permeability in Silurian Carbonate Rocks of Hunton Group, Anadarko Basin, Oklahoma: ABSTRACT

Author(s): T. W. Amsden

Article Type: Meeting abstract

Abstract:

Ninety Hunton cores have been studied, from which 82 Silurian samples from 22 wells were tested for porosity and permeability. Each sample was examined in thin section and was chemically analyzed for CaCO3, MgCO3, and HCl insolubles. The specimens range from limestone and calcareous mudstone having less than 1% MgCO3 to crystalline dolomite with more than 43% MgCO3. Porosity ranges up to 21%, and permeability to 305 md. Rocks with appreciable porosity and permeability have a circumscribed range in texture and composition--specimens with more than 5% porosity are confined to crystalline dolomites with more than 35% MgCO3 (65% dolomite), and those with more than 10% porosity to dolomites with more than 37% MgCO3 (80% dolomite). Much of the pore space is in the form of fossil molds and vacuities in the matrix surrounding oolites. The fossil molds are due to leaching, and the porous oolites probably result from a primary porosity increased by dissolution. Not all dolomites have high porosity, and several specimens with more than 35% MgCO3 have less than 1% porosity; the latter condition appears to result at least in part from preservation of the fossils by calcspar and dolospar rather than as molds. Leaching of fossils and preservation by spar are confined to crystalline dolomite, thus indicating a genetic relation to dolomitization. A suggested sequence of events in the development of porosity is dolomitization and leaching, followed by some secondary cementation of pore space by sp r.

Present information indicates a geographic concentration of these porous Silurian dolomites in the north-central and western parts of the Anadarko basin in Oklahoma.

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