Current Abstract
December 9th, 2025 Meeting Abstract
“Exploration in the Deepwater Gulf of Mexico – 50 Years In“
Presented by:
Daniel C. Steward
Abstract:
The Deepwater Gulf of Mexico (DWGOM) contains a prospective area of +/- 68,000
square miles, multiple source rocks though primarily Jurassic (Tithonian), a target
reservoir section from the Jurassic to the Pleistocene with gross basin thicknesses
approaching 50,000’ – all leading to 4 major play types active today. The extensive
Jurassic Louann Salt provides the ultimate deformable substrate at the bottom of this
immense stratigraphic pile, consequently deformed in myriad ways. This galactic
combination of favorable ingredients for generating and trapping hydrocarbons has and
will keep many geologists and geophysicists busy for decades to come as the DWGOM
is forecast to produce above 2 million barrels of oil equivalent gas (BOEG) per day in
the coming years. More than 800 exploration wells have been drilled in the last 50
years pursuing, in broad categories: 1) amplitudes, 2) subsalt Miocene, 3) lower Tertiary
Wilcox, including subsalt, and 4) Jurassic Norphlet. In July of 1975, at a water depth
1,025’, Shell discovered the Cognac field in Mississippi Canyon 194, ushering in both
the deepwater and amplitude plays. The pursuit of “hot amplitudes” or “bright spots”
took off and has thus far netted 556 wildcat wells, 8.5 billion BOEG in 181 fields – a
32.5% success rate for commercial production. The amplitude trend’s field sizes have
declined over time as the play has matured but the allure of a single well producing
more than 80 million BOEG remains. Exploration creativity along with significant
technological advances in seismic acquisition and processing with novel deep water
and deep depth drilling capabilities allowed exploration to proceed into deeper water
and deeper prospective sections over extremely broad areas within the DWGOM. The
hints of a subsalt play emerged when an outer GOM Shelf wildcat accidentally pierced
salt and encountered sand. The Mahogany field at South Timbalier 370 found subsalt
pay in 1993. In other areas of the DWGOM seismic stratigraphy clearly showed
significant sedimentary sections beneath salt. Hence, Exxon drilled the first deepwater
(4,358’) subsalt discovery at Mississippi Canyon 211 in May of 1990 in what would
become the Mica field. Subsequent subsalt exploration, based solely on structural
mapping on ever-improving 3D seismic data sets, has led to 121 subsalt wildcats with
40 discoveries and a minimum of 5.7 billion BOEG at a 33% commercial success rate.
Unlike the comparatively modest depths of the amplitude trend, the average well depth
of all subsalt wells is greater than 26,000’ drilled on locations with an average water
depth of 4,813’. The lower Tertiary Wilcox trend emerged within exploration portfolios
leased on Miocene ideas with a poignant lesson on the importance of penetrating the
entire prospective section. Further structural mapping with key seismic stratigraphy
observations, an 100% success rate, and a near basin-wide play fairway, propelled the
Wilcox play to the forefront in terms of future material resource additions. The trend has
yielded at least 5.4 billion BOEG in 22 successful wildcats out of a total of 69, a 31.8%
success rate. The Jurassic Norphlet, the newest trend of the four, targets aeolian
reservoirs in the thick Mesozoic sections of eastern Mississippi Canyon and western
DeSoto Canyon. Thus far the trend has produced 6 discoveries with 1.1 billion BOEG
aggregate out of 21 total wells for a 28.5% exploration success rate. In this panoply of
activity with a stunning amount of monetary resource involved, the importance of a
disciplined exploration process cannot be over-emphasized as demonstrated in
tremendous success stories and heart-breaking failures, in both the pre-drill, cost-
intensive Federal lease sales, data purchases, and finally in part or all of the answer in
the drilling outcomes.
Biography:
Dan, a native of Taft, California and alumni of CSU, Bakersfield (BS & MS Geology) and
Rice University (MBA), is the current president of the Pacific Section of the American
Association of Petroleum Geologists and president of the Los Angeles Basin Geological
Society since 2022. Dan currently runs Iron Horse Consulting from their home in
Corona, California. His free time is divided between the family real estate businesses,
their four college-age daughters’ goings-on, volunteering with the Section and Society,
hitting the mountain bike trails, pursuing intriguing geological phenomenon that he never
had time for, both surface and subsurface, and enjoying the company of family and
friends far and wide. In his 26-year professional career, Dan worked for Arco
Exploration, Chevron (both in Bakersfield); Noble Energy, Lukoil International, Total, Iron
Horse Energy LLC, and Amplify Energy (Houston & Long Beach). These experiences
covered the San Joaquin Basin (SJB), the Los Angeles Basin, the deepwater Gulf of
Mexico (U.S. & Mexican areas), the west African margin (Cameroon, Equatorial Guinea,
Sierra Leone, Cote d’Ivoire, Ghana) , the Black Sea (Romania), the Barents Sea
(Norway), and various proved-developed-producing pursuits in the Salinas Basin, on the
Permian Shelf of eastern basin by the same name, and the SJB. Dan and his wife
Sandra and three of their four daughters relocated to California from The Woodlands,
Texas in 2019 and remain extremely happy to be back in their home state.