5. Geologic Controls on Hydrocarbon Resources in Fractured Ordovician Carbonate Strata, and Implications for Future National Energy Supply

The USGS mission of assessing the oil, gas, and coal resources of the United States is dependent upon understanding energy systems and the complex relations between source rocks, maturation, migration pathways, traps, and seals. Although the United States has an abundance of fossil fuels, energy reserves are being depleted and environmental restrictions limit the amount of resources available for extraction and combustion. This depletion of energy reserves necessitates a focus on areas of greater hydrocarbon potential, although proximity to population areas presents potential conflicts with land use issues and with contamination of water resources. Nevertheless, a detailed and timely understanding of the Nation's hydrocarbon resources is critical for evaluating future energy supply options and the environmental consequences of their development.

The greatest potential for undiscovered hydrocarbon resources in eastern North America (where much of the population resides) is within the Ordovician Trenton-Black River carbonates and equivalent strata. These strata extend from the Permian Basin in Texas, through the Anadarko, Arkoma, Illinois, Michigan, and Appalachian Basins, and into eastern Canada. Some of the larger oil fields in the United States have been discovered in Trenton-Black River strata in Michigan (e.g., >100 million barrels from the Albion-Scipio Field; discovered 1957), and yet these strata are relatively under-explored in much of the eastern United States. Recent hydrocarbon discoveries in the Trenton-Black River strata in New York have generated a great deal of renewed interest and activity in the Appalachian Basin.

Hydrocarbon accumulations in the Ordovician Trenton-Black River strata are widespread, but poorly understood. Most of the reservoirs consist of fractures in otherwise low-permeability carbonates (with some thin beds of shale and bentonite), and the fractures are associated with hydrothermal dolomite and lead-zinc minerals. These fractured reservoirs may be several miles long, but widths are typically on the order of a few hundred feet. Consequently, the reservoirs are difficult to resolve in seismic data, thus making it extremely difficult to identify undiscovered reservoirs. Because of these difficulties in identifying reservoirs in seismic data, the Ordovician Trenton-Black River strata are relatively under-explored and they still have great potential for undiscovered hydrocarbon resources.

Under this Research Opportunity, applicants are invited to conduct an integrated analysis of the fractured Ordovician Trenton/Black River reservoirs in the Appalachian, Michigan, and (or) Illinois Basins. The research will include integration and interpretation of information from seismic data, outcrops, hydrocarbon wells, water wells, petrographic and petrophysical data, and other geologic data as needed. In particular, the mapping of thermal maturity data (i.e., vitrinite reflectance, condont color alteration indices) and Total Organic Carbon contents of interfingering and adjacent shales will be used to delineate regions of viable hydrocarbon source rock. Other data will be used to characterize reservoir distributions and characteristics, hydrocarbon trapping mechanisms, and the nature of fluid contacts. In addition, the roles of sequence stratigraphy (carbonate cyclicity), diagenesis, and the distribution of bentonites may be investigated for possible influences on the movement of hydrocarbons and other fluids through these Ordovician carbonate strata. The compilation and analysis of various data from these fractured carbonate reservoirs should (1) aid in the prediction of reservoir distributions and characteristics, (2) increase our understanding of the history and nature of fluid flow (hydrocarbons, water, mineral-bearing fluids) through these strata, and (3) improve the ability of the USGS to assess the quantity and quality of yet undiscovered hydrocarbon resources in these strata.

The postdoctoral candidate should be able to work on a variety of scales ranging from basin tectonics and stratigraphic framework, to microstructural and petrographic issues. In addition, the research should build on previous work by DOE, GRI, and academia, and could lead to possibilities for interdisciplinary collaboration with hydrologists (especially in areas such as east-central Kentucky, where oil in these strata is present near the surface) and mineral resource geologists (i.e., lead-zinc deposits). Research conducted under this opportunity will increase our understanding of the tectonic, sedimentary, burial history, and fluid flow processes that control hydrocarbon generation and fluid movements in these Ordovician reservoirs. Candidates for this opportunity must have a strong background in the principles of petroleum geology, sedimentology, and sequence stratigraphy. Expertise in appropriate regional geology would be an additional benefit, as well as experience with petroleum exploration databases. Proposed Duty Station: Reston, VA

Areas of Ph.D.: Petroleum geology, stratigraphy, sedimentology, structural geology

Qualifications: Applicants must meet one of the following qualifications: Research Geologist

(This type of research is performed by those who have backgrounds for the occupations stated above. However, other titles may be applicable depending on the applicant's background, education, and research proposal. The final classification of the position will be made by the Personnel specialist.)

Research Advisor(s): Christopher Swezey, (703) 648-6444, cswezey@usgs.gov; John Repetski, (703) 648-5486, jrepetski@usgs.gov

Personnel Office contact: Rosetta Alexander, (703) 648-7468, ralexand@usgs.gov

Summary of Opportunities