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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 66 (1982)

Issue: 9. (September)

First Page: 1423

Last Page: 1423

Title: Saddle Crystal Dolomites as Fractured Reservoir Indicators, Mississippian Biohermal Facies, Hardeman County, Texas: ABSTRACT

Author(s): Wayne M. Ahr

Article Type: Meeting abstract

Abstract:

Dolomitized Mississippian biohermal facies in the Hardeman basin of Texas produce mainly from fractures. During Osagian time, crinoid-bryozoan mud mounds were common in the shallow basin. In several field areas, early dolomitization, leaching, solution brecciation, and silicification occurred episodically during the development of the muddy, biohermal core sequences. Subsequent burial diagenesis involved calcite cementation, pressure-solution, several stages of fracturing, and a late stage of dolomitization. The dolomite consists of saddle crystals that lined early vugs and fractures and replaced skeletal grains. The dolomite has ^dgrO18 values of -10 to -12 (PDB) and originated in the subsurface after fracturing occurred. It is readily distinguished in cutting , making it a fracture-vug indicator that is identifiable at the well site. As the Quanah field reservoir and many others in the area owe their permeability mainly to fractures, the saddle crystal dolomites identify the primary productive zones and may enable the mapping of permeability trends.

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Copyright 1997 American Association of Petroleum Geologists