Oil geochemistry plays a critical role in all modern petroleum exploration programs in the Gulf of Mexico. This article provides a brief history of Gulf of Mexico oil geochemistry research.
Currently routine applications of oil geochemistry in the Gulf of Mexico include:
- Assessing charge risk prior to drilling (using oil geochemistry and basin modeling)
- Identifying pay zones in new wells (e.g., using geochemical mud-gas logging)
- Characterizing the petroleum systems responsible for an oil show or discovery (using biomarker analyses of shows or produced oils)
- Determining reservoir compartmentalization
- Identifying completion problems in wells
Brief history of Gulf of Mexico Oil Geochemistry Research
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 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 reservoir 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.
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" to conduct a project. Fortunately, more than 3,000 Gulf of Mexico produced oil, seep oil, and piston core samples are available for analysis in the Weatherford Oil Library/Data Room. This database may contain the samples needed to make a project feasible. For many of the samples, data have already been analyzed, and those data are available for sale.
For more information on the techniques described here, or to discuss a specific project, e-mail us at firstname.lastname@example.org, or
call us at U.S. (214) 584-9169.
Beeunas, M. A., M. Schoell, and J. Zumberge, 2001, Habitat of Natural Gas in the Gulf of Mexico Shelf: 2001 AAPG Annual Convention Program with Abstracts: v. 10, p.A15.
Bissada, K. K., B. J. Katz, S. C. Barnicle, and J. D. Schunk, 1990, On the origin of hydrocarbons in the Gulf of Mexico Basin-a reappraisal, in D. Schumacher and B. F. Perkins, eds., Gulf Coast oils and gases, their characteristics, origin, distribution, and exploration and production significance: Gulf Coast Section SEPM Foundation Ninth Annual Research Conference, p. 163-171.
Cole G. A., R. Requejo, J. DeVay, A. Yu, F. Peel, J. Brooks, B. Bernard, J. Zumberge, S. Brown, 2001, Deepwater Gulf Of Mexico Piston Coring: Seepage Versus Anomalies Versus Background And Relationship To The Deepwater GOM Petroleum System: AAPG Bulletin, v. 85, No. 13. (Supplement).
Cole, G A., A. Yu, F. Peel, J. Brooks, B. Bernard, J. Zumberge and S. Brown, 2002, Deepwater Gulf of Mexico - Using Seepage and Oils to Understand the Source and Charge Issues: Gulf Coast Association of Geological Societies, Transactions, v. 52, p.134.
Curtis, D. M., 1989, A conceptual model for sources of oils in Gulf Coast Cenozoic reservoirs: Gulf Coast Association of Geological Societies Transactions, v. 39, p. 37-56.
Guzman-Vega, M. A., L. Castro Ortiz, N, Canipa Morales, J. R. Roman Ramos, L. Medrano Morales, C. Valdez, E. Vazquez Covarruvias and G. Ziga, 2002, The Origin of Oil in the Mexican Coast Basins in the GOM: Gulf Coast Association of Geological Societies, Transactions, v. 52, p. 364.
Herbin, J. P., G. Deroo, and J. Roucache, 1983, Organic geochemistry of Lower Cretaceous sediments from Site 535, Leg 77: Florida straits, in R. T. Buffler et al., Initial reports of the Deep Sea Drilling Project, Leg 77: Washington, D.C., U.S. Government Printing Office, p. 459-474.
Nunn, J. A., and R. Sassen, 1986, The framework of hydrocarbon generation and migration, Gulf of Mexico continental slope: Gulf Coast Association of Geological Societies Transactions, v. 36, p. 257-262.
Oehler, J. H., 1984, Carbonate source rocks in the Jurassic Smackover trend of Mississippi, Alabama, and Florida, in J. G. Palacas, ed., Petroleum geochemistry and source rock potential of carbonate rocks: AAPG Studies in Geology 18, p. 63-70.
Patton, J. W., P. W. Choquette, G. K. Guennel, A. J. Kaltenback, and A. Moore, 1983, Organic geochemistry and sedimentology of lower to mid-Cretaceous deep-sea carbonates, Sites 535 and 540, Leg 77, in R. T. Buffler et al., Initial reports of the Deep Sea Drilling Project, Leg 77: Washington, D.C., U.S. Government Printing Office, p. 417-443.
Peters, K. E., and J. M. Moldowan, 1993, The Biomarker Guide, Interpreting molecular fossils in petroleum and ancient sediments: Prentice Hall, 363 p.
Sassen, R., 1990, Geochemistry of carbonate source rocks and crude oils in Jurassic salt basins of the Gulf Coast, in J. Brooks, ed., Classic petroleum provinces: Geological Society Special Publication 50, p. 265-277.
Sassen, R., and C. H. Moore, 1988, Framework of hydrocarbon generation and destruction in eastern Smackover trend: AAPG Bulletin, v. 72, p. 649-663.
Sassen, R., R. S. Tye, E. W. Chinn, and R. C. Lemoine, 1988, Origin of crude oil in the Wilcox trend of Louisiana and Mississippi: evidence of long-range migration: Gulf Coast Association of Geological Societies Transactions, v. 38, p. 27-34.
Sassen, R., and E. W. Chinn, 1990, Implications of lower Tertiary source rocks in south Louisiana to the origin of crude oil, offshore Louisiana, in D. Schumacher and B. F. Perkins, eds., Gulf Coast oils and gases, their characteristics, origin, distribution, and exploration and production significance: Gulf Coast Section SEPM Foundation Ninth Annual Research Conference, p. 175-179.
Sassen, R., J. M. Brooks, M. C. Kennicutt, I. A. MacDonald, and N. L. Guinasso, 1993, How oil seeps, discoveries relate in deepwater Gulf of Mexico: Oil & Gas Journal, v. 91, p. 64-69.
Walters, C. C., and D. D. Dusang, 1988, Source and thermal history of oils from Lockhart Crossing, Livingston Parish, Louisiana: Gulf Coast Association of Geological Societies Transactions, v. 38, p. 37-44.
Wenger, L. M., R. Sassen, and D. Schumacher, 1990, Molecular characteristics of Smackover, Tuscaloosa, and Wilcox-reservoired oils in the eastern Gulf Coast, in D. Schumacher and B. F. Perkins, eds., Gulf Coast oils and gases, their characteristics, origin, distribution, and exploration and production significance: Gulf Coast Section SEPM Foundation Ninth Annual Research Conference, p. 37-57.
Wenger, L. M., L. R. Goodoff, O. P. Gross, S. C. Harrison, and K. C. Hood, 1994, Northern Gulf of Mexico, an integrated approach to source, maturation, and migration: First Joint AAPG/Asociacion Mexicana de Geologas Petroleros Hedberg Research Conference Program, 6 p.
Zumberge J., H. Illich, C. Pratsch, N. Cameron, J. Brooks, and S. Brown, 1999, Origin of Oil in the Gulf of Mexico: Exploration and Exploitation Significance: AAPG Bulletin, v. 83, p. 1296-1346.