Because the oil source rocks in the offshore Gulf of Mexico and
particularly in the deepwater areas are below current well
penetrations, authentic samples of mature petroleum source rocks
have rarely been directly collected from the offshore Gulf of
Mexico. However, recent oil geochemistry studies have inferred
relatively specific petroleum source intervals (stratigraphic and
aerial distribution) from the geochemistry of produced oils,
produced gases, oil seeps and gas seeps (e.g., Cole et al., 2002;
Guzman-Vega et al., 2002; Beeunas et al., 2001; Cole et al., 2001;
Zumberge et al., 1999).
In the 1980's and early 1990's, workers began to use oil
geochemistry techniques to correlate onshore oils in Louisiana
and Texas to specific source rock intervals in areas where
authentic mature petroleum source rock intervals had been reached
by the drill bit (Oehler, 1984; Sassen and Moore, 1988; Sassen et
al., 1988; Walters and Dusang, 1988; Sassen, 1990; Sassen and
Chinn, 1990; Wenger et al., 1990). Also in the early 1980's, the
Deep Sea Drilling Project at Sites 535 and 540 in the Florida
straits penetrated organic-rich (albeit thermally immature) shales
which several studies characterized (Herbin et al., 1983; Patton et
al., 1983).
In the late 1980's to the mid-1990's workers began to integrate
the results of earlier studies with new geochemical data from
thousands of seep oils collected by piston cores from the deepwater
Gulf of Mexico. Also about this time, tested oils from recent
deepwater discoveries were becoming available for analysis.
The resulting new studies, aided by these newly acquired deep
water samples, provided the foundation for our current
understanding of the petroleum systems of the greater Gulf of
Mexico (e.g., Nunn and Sassen, 1986; Curtis, 1989; Bissada et al.,
1990; Sassen and Chinn, 1990; Sassen et al., 1993; Wenger et al.,
1994). The results of these studies have established and in some
cases inferred the sources of reservoired oils to be organic
carbon-rich rocks of the Triassic, Oxfordian, Tithonian, Aptian,
Turonian, and Eocene in the greater Gulf of Mexico basin. The
relative importance of these discrete sources varies laterally in
the basin. As a result, oil geochemistry is now a routine part of
prospect risk assessment in the Gulf of Mexico.
Currently routine applications of oil geochemistry in the Gulf
of Mexico include:
Although oil geochemistry and gas geochemistry can be used to
solve a variety of Gulf of Mexico exploration and development
problems, such projects require access to oil, rock, and/or gas
samples. However, a company which needs these data may not have all
the samples "in house" needed to conduct a project. Fortunately, Over
3900 Gulf of Mexico produced oil, seep oil, and piston core
samples are available for analysis in various oil collections
that can be searched using the on-line OilTracers Oil
Library. This database can lead you to the samples needed to
make a project feasible. For many of the samples, data have already
been acquired by the laboratories that own the samples, and those
data are available for sale.
For more information on applying oil geochemistry to petroleum
exploration in the Gulf of Mexico, or to discuss a specific
project, e-mail us at info@oiltracers.com, or call
us at U.S. (214) 584-9169.
References
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1990, On the origin of hydrocarbons in the Gulf of Mexico Basin-a
reappraisal, in D. Schumacher and B. F. Perkins, eds., Gulf Coast
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Bernard, J. Zumberge, S. Brown, 2001, Deepwater Gulf Of Mexico
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