Abstract: Norphlet Geology and 3-D Geophysics
of Fairway Field
Mobile Bay, Alabama
STORY, CHIP
Amoco Corporation, 501 WestLake
Park Blvd., Houston, TX
The Upper Jurassic Norphlet system in the Mobile Bay area has
been the subject of considerable exploration
intrigue during the last 20
years Fairway Field, which came on production in December 1991, lies in
the restricted access area of the main Mobile Bay shipping fairway leading
to the city of Mobile, Alabama and is comprised of state blocks 113 and
132.
The exploration
and exploitation of the area south of Dauphin Island
has been based primarily on the geophysical evaluation of a high quality
3-D seismic survey shot by an industry consortium in 1986 to image the
eolian Norphlet unit at depths between 21000 and 22000 ft. Seven thousand
line mi of data were recorded over an area of about 250 sq. mi and covers
all or parts of 49 state and federal offshore blocks.
The enhancement provided by 3-D imaging to the geometric resolution
of the lenticular Norphlet dune trends in this area is significantly better
than with 2-D data. The concave base of the Norphlet/top of Louann event
was essentially unmappable with 2-D imaging. An accurate understanding
of the thick lenticular nature of the dune trends therefore did not exist
pre3-D. The 3D imaging has led to a much better regional understanding
of the unique depositional environment of the Norphlet and consequently
to a much improved post-3-D interpretation of the Shell/Amoco Fairway Field.
The Norphlet isopach has been mapped with confidence and has led to the
interpretation of a series of northwest-southeast trending linear dune
forms across the survey area. Post-3-D exploration
methodology has targeted
these thick, paleogeomorphic features where they have been enhanced by
subjacent salt structure.
AAPG Search and Discovery Article #90932©1998 GCAGS/GCS-SEPM Meeting, Corpus Christi, Texas