ABSTRACT

A combination of inland dune and wadi-style deposition of alluvial sands and gravels is providing a re-vitalized play to the Norphlet Formation (Jurassic) of southwest Alabama. In the same area where operators were successful several years ago in establishing Frsico City (Haynesville) reservoirs in pinchouts high on basement structures; recent drilling lower on the flanks of these same structural complexes is providing similar results.

Facies interpretation of conventional core data and 3-D seismic each play a very important role in making this rend economic and attractive. High well success rates and test rates ranging from 300-500 barrels of oil and 1000 MCF gas per day make these 11,000-12,000 foot targets a viable exploration venture.

The Norphlet reservoirs are composed of a fining upwards succession of gravelly alluvial fans, braided streams and ephemeral (1-6 foot thick) eolian dunes. This continental sand and gravel assemblage was re-worked during subsequent Smackover transgression. A thin upper Nophlet fan delta and coastal tidal flat facies is recognized beneath and interfingering with basal laminated lime muds of the lower Smackover Formation.

The most attractive reservoir properties have thus far been located in the eolian dune and re-worked shallow marine environments. Marine carbonate cementation in the upper sands, and differential compaction in the lower gravelly sands are the primary distructional aspects to reservoir porosity and permeability. In addition, the localized occurrence of unstable volcanic rock fragments provide a source of authigenic clays which require consideration during completion techniques.

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