Upper Jurassic Smackover Stratal Relationships of the Little Cedar Creek and Brooklyn Fields and Possible Embayment Wide Microbolite Buildups in Southwest Alabama
Kyle L. Day and William C. Parcell
Department of Geology, Wichita State University
This study investigates the stratal relationships of a pure microbolite within the Upper Jurassic strata at the Little Cedar Creek, and Brooklyn Field complex for the development of a refined exploration model of Smackover reefal buildups in the eastern Gulf Coast. During the Jurassic, southwestern Alabama was divided by Appalachian ridges into three sub-basins: the Conecuh Embayment, Manila Embayment, and the eastern extension of the Mississippi Interior Salt Basin. The complex is located in the Conecuh Embayment of southeastern Conecuh County, Alabama, and are the largest fields discovered in the state of Alabama. Production from the fields is currently over 27 million barrels of oil and over 28 billion cubic feet of gas. The microbolite buildups formed in an inner ramp setting of the Upper Jurassic (Oxfordian) Smackover Formation.
The Little Cedar Creek and Brooklyn Field are anomalous discoveries compared to other oil and gas fields in the region. Previous studies observed that microbial nucleation occurred on Paleozoic crystalline basement highs where depositional fabrics were heavily modified by dolomitization. Instead, the complex’s microbolite buildups developed on mudstones, have no apparent association with paleo-highs, and have retained a large percentage of original depositional fabrics.
The study (1) examines the basal contacts of the microbolite using well logs, well core, and petrographic analysis with the hopes of refining conceptual models of the controls on microbial nucleation, (2) addresses the possibility of microbolite development across the Conecuh sub-basin and (3) develops a model that incorporates depositional and diagenetic settings for the region.
AAPG Search and Discovery Article #90182©2013 AAPG/SEG Student Expo, Houston, Texas, September 16-17, 2013