A Deepwater Frontier in the North-Eastern Gulf of Mexico: The Jurassic Norphlet Sandstone Oil Play

Jessica McDonough, Ryan T. Murphy, Robin S. Pilcher, and Caroline Burke
Hess Corporation, Houston, TX

Eolian sandstones of the Jurassic Norphlet Fm. are a proven gas play along the south-eastern US Gulf Coast. Recent industry drilling demonstrates Norphlet play potential in deepwater ~170km offshore. Our analysis suggests that a Norphlet oil play extends at least 230km farther south-east in a belt up to 100km wide directly outboard of the Florida Escarpment. Regional well data and seismic interpretation underpin our study which integrates structural analysis, seismic stratigraphy, and petroleum system modeling to delineate and characterize critical play elements.

The structural setting of the Norphlet oil play is a series of Jurassic raft blocks which detached and translated basin-ward on the Louann Salt. Jurassic reservoir (Norphlet Fm. eolian sands) and source rock (Smackover Fm. marine marls) are structurally segmented and entirely contained within raft blocks. Rafts are separated by salt ridges and/or extensional fault gaps containing upper Jurassic and lower Cretaceous growth strata. This structural style is analagous to parts of the Angolan and Brazilian passive margins.

Seismic stratigraphy elucidates depositional stacking patterns and reservoir potential within individual rafts. Burial history and thermal modeling suggest variation in reservoir quality and source rock maturity. Additional source rock modeling predicts fluid properties and charge volumes. Reservoir deliverability rates are derived from fluid properties and reservoir quality parameters. We combine structural and stratigraphic analysis of the raft blocks with petroleum system modeling to define higher potential trends within the overall play area.

Recent deepwater exploration in the Gulf of Mexico has focused on Neogene and Paleogene targets. The Jurassic Norphlet oil play in the deepwater north-eastern Gulf represents an emerging extension of a mature onshore and continental shelf gas play.

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