--> ABSTRACT: A Model for Quartz Cementation in the Norphlet Formation, Mobile Bay, Offshore Alabama, by J. M. Ajdukiewicz; #91020 (1995).

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A Model for Quartz Cementation in the Norphlet Formation, Mobile Bay, Offshore Alabama

J. M. Ajdukiewicz

The Jurassic eolian Norphlet Formation, in Mobile Bay, offshore Alabama, is characterized by a quartz-cemented tight zone that occurs ubiquitously at the top of the formation, varying in thickness from 20 to 200 ft from well to well. Prediction of the tight-zone thickness distribution between wells is important to well placement and reserves calculations. An integrated reservoir-quality study combining petrographic data from 450 thin sections in 23 wells with burial-history, fluid-flow, and geochemical modeling resulted in a model for the formation and distribution of this tight zone. Our observations indicate that the tight-zone formation was not related to depositional environment, coupled pressure-solution/quartz precipitation, marine reworking, or fluid convection. An alternate model relating quartz cementation to geochemical conditions within overmaturing early oil reservoirs has had significant success in predicting tight zone thickness over much of Mobile Bay.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995