SMITH, CHARLES C., and ROBERT M. MINK

The discovery of shallow Miocene gas in southwestern Baldwin County, Alabama, in 1979 has led to an active and successful Miocene exploration program throughout southern Alabama and its adjoining State waters area. Since 1986, when Miocene gas was detected in the southern portion of Mobile Bay, seven Miocene natural gas fields have been established in Alabama State waters with current active production exceeding 68 billion cubic feet. This production is from the middle Miocene Amos sand and the more recently discovered upper Miocene Dauphin sand.

In 1990, natural gas was found in the Dauphin sand in the Mississippi Sound area north of Dauphin Island. To date, 12 Dauphin sand wells in four upper Miocene fields in offshore Alabama have produced over 65 billion cubic feet of natural gas, 95% of the total production of all other Miocene fields in Alabama State waters. The majority of this gas, over 57 billion cubic feet, has been produced from the North Dauphin Island Field. The Dauphin sand lies at depths of approximately 1,500 feet and is biostratigraphically within the upper part of the Discorbis "12" Interval Zone of middle late Miocene age. Reservoirs most commonly consist of shallow marine, inner and middle neritic elongate offshore bars. Production is from combination traps involving sand porosity and permeability pinchouts along regional dip. The hydrocarbon type is methane gas of predominantly biogenic origin. Evaluation of relative amplitude seismic data is the primary means of exploring for these Dauphin sand natural gas reservoirs.

AAPG Search and Discovery Article #90941©1997 GCAGS 47th Annual Meeting, New Orleans, Louisiana