Exploration Implications of
Oil
and Natural
Gas
Seepage in
Frontier Areas of the Louisiana-Texas Continental Slope, Northern Gulf of Mexico
Alan S. Kornacki, John W. Kendrick, John L. Berry
The occurrence, distribution, and chemistry of crude
oil
and natural
gas
seeps along the upper Louisiana continental slope have been used to help
recognize and appraise the exploration potential of this frontier area. The
presence of deepwater
oil
seeps was first established more than 25 years ago by
the 'Eureka Program', a pioneering effort undertaken by Shell
Oil
Company that
involved drilling coreholes above shallow salt bodies. Subsurface
oil
seeps were
encountered at seven deepwater locations. Three Eureka seeps in the Green Canyon
lease area occur downdip of
oil
discoveries at Bullwinkle and Vancouver. Even
more intriguing, a cluster of subsurface
oil
seeps was identified on the south
Texas continental slope in the Alaminos Canyon 970-971 blocks, 155 miles
southwest of the nearest significant offshore
oil
production (at the Snapper
Field).
Oil
discoveries in water depths significantly >3000 ft have been reported
only in the eastern Mississippi Canyon lease area. But
oil
and natural
gas
seepage is very common along the middle to lower Louisiana slope in the southern
Garden Banks and north-eastern Keathley Canyon lease areas in water depths as
great as 6000 ft, downdip of commercial petroleum discoveries at Auger,
Bienville, and Cooper. These seeps demonstrate
oil
charge in a largely
unexplored deepwater area off the coast of western Louisiana.
Other than proving regional charge, the presence of petroleum seeps near an
untested deepwater prospect does not appear to materially aid in evaluating the
likelihood that a commercial
oil
or
gas
accumulation exists in the subsurface.
Prospect appraisal requires the performance of careful trap, seal, and reservoir
analyses, plus an assessment of the vertical and lateral components of petroleum
migration into the prospect.
AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995
