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Effect of Dolomitization and Diagenetic Overprint on Microbial Fabric Characterization, Southwest Alabama

Peter Wheiland

This study compares Smackover microbial limestone fabrics from Little Cedar Creek Field (LCCF), Conecuh County to equivalent dolomitized strata at nearby Appleton Field, Escambia County, Alabama. Microbial carbonate buildups are proven petroleum reservoirs in southwest Alabama, including Appleton, Vocation and Little Cedar Creek Fields. For the past 30 years, extensive effort has been applied to describing these microbial fabrics because of their influence on reservoir quality variability. Various classifications of microbial fabrics have also provided models for interpreting depositional history and stratigraphic position of these buildups. However, these classifications have been applied to strongly dolomitized buildups at Appleton and Vocation Fields. The Smackover at Little Cedar Creek Field in Conecuh County displays microbial facies and reservoirs in a largely undolomitized state. These strata are an ideal dataset to characterize original microbial textures, providing more pristine information to interpret depositional environments and determine the extent that original depositional fabric controlled final reservoir quality. Cores and well data reports are used to characterize LCCF microbial fabrics. Associated reservoir qualities are compared to previous classifications of dolomitized microbial fabrics at Appleton Field. Discriminating between dolomitized vs nondolomitized microbial fabrics will provide more robust interpretations of depositional environments and build a history of the transition and extent that fabric controls reservoir quality as diagenetic processes took effect on these strata. 

AAPG Search and Discovery Article #90176©AAPG Mid-Continent Meeting, Wichita, Kansas, October 12-15, 2013