Depositional Analysis of the Jurassic Norphlet Formation in Mississippi: Impact on Petroleum Potential Offshore
Jessee, Marcus L.; Weislogel, Amy
The Norphlet Formation is an Upper Jurassic syn-rift clastic reservoir in the Gulf of Mexico that was deposited conformably in most areas atop the Louann Salt and which is overlain by the carbonate Smackover Formation, which serves as the petroleum source rock. Recent discoveries in the offshore eastern Gulf of Mexico, atop the Appomattox structure in the Shiloh and Vicksburg wells drilled by Shell and Nexen have renewed interest in the Norphlet Formation as a petroleum play. The Norphlet Formation is a proven reserve in both the onshore Gulf coast as well as the offshore central Gulf of Mexico area. Late Jurassic basin geometry and paleogeography, and their effect on petroleum potential is essential for accurately assessing risk as well as developing a successful exploration strategy for Norphlet plays. A detailed study of the onshore Norphlet Formation in Mississippi, which includes U-Pb detrital zircon geochronology, heavy mineral analysis, and sandstone petrology, along with well log and core analysis are used to create a stratigraphic architecture. The results yield reconstruction of facies distribution, lithologic variation, and sediment transport pathways. Previous work on the Norphlet Formation in onshore Alabama and adjacent federal waters has shown that sediment source varies spatially, with northern sediments originating from relict Appalachian Mountains and reworked foreland basin strata as well as erosion of the Suwannee terrain. This work suggests the possibility of mixing sediment from multiple sources in the Norphlet formation, as well as the possibility of previously undocumented influx of cratonal-derived sediment predominately northwestern areas of the EGOM, with increased mixing of sediment sources to the south as a result of increased sediment input from erosion of the relic Appalachian Mountains. Identification of this new potential sediment source further illustrates the complexity of Norphlet formation deposystem but allows for more accurate constraints on the depositional history. By identifying this new sediment source and integrating it with previous data as well as other parameters, such as facies variations, thickness paleoclimate and paleotopography we can further define the constraints used in stratigraphic forward modeling of the area. The results of this study are placed in context with available production data to better constrain reservoir characteristics of the Norphlet Formation.
AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013