ABSTRACT

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 1982, when Upper Miocene gas was discovered in the southern portion of Mobile Bay, four Discorbis "12" Interval Zone Dauphin sand natural gas fields have been established in Alabama State waters. The Discorbis "12" Interval Zone generally consist of sediments which accumulated in transitional to inner neritic paleoenvironmental settings. The natural gas productive Dauphin sand usually occurs within 90 m of the top of the Discorbis "12" Biohorizon and was deposited in shallow-marine and relatively high energy beach and nearshore bar deposits.

The combined cumulative production from the North Dauphin Island, Northwest Dauphin Island, Northeast Petit Bois Pass, and South Dauphin Island Fields exceeds 66 billion cubic feet of gas. This gas has been produced from depths between 520 to 610 m. Production is from a combination of traps involving sand porosity and permeability pinchouts along regional dip or across anticlinal nosing trends. The hydrocarbon type is methane gas of predominately biogenic origin. Evaluation of relative amplitude seismic data is the primary means of exploring for these Dauphin sand natural gas reservoirs.