U.S. Geological Survey
Energy Resource Surveys Program
USGS Fact Sheet FS-021-97
"Specialized chemistry and mineralogy laboratories in the U.S. Geological Survey conduct research that promotes our understanding of the formation and location of energy commodities. This information is crucial to decisionmaking related to our changing energy mix. Geochemistry also provides a tool for understanding the environmental consequences of finding, extracting, and using energy sources, thereby facilitating more effective mitigation strategies."Dr. George Breit, Dr. Michele Tuttle, Dr. Gene Whitney, U.S. Geological Survey
U.S. Geological Survey (USGS) research labs conduct fundamental geochemical research.
USGS scientists have achieved significant advances in geochemistry analysis as they conduct experimental and field studies in energy-source characterization and environmental processes. Numerous studies underway include interpreting the history of sedimentary basins, global climate change, geochemistry of mineralizing systems, thermal maturation of hydrocarbon source rocks, and tracking the disposition and ultimate fate of contaminants in the environment. Scientists also provide training to other researchers in the use of specialized equipment and application of new techniques developed for these investigations.
Important USGS research now links bacteria to the formation of certain hydrocarbon deposits.
Recent studies indicate that the activity of microorganisms in organic-rich rocks promotes formation of sulfide ores and generation of hydrocarbons. Laboratory experiments suggest that magnetic signatures of biological reaction products mimic magnetic signatures observed around hydrocarbon accumulations, such as those seen on the North Slope of Alaska.
USGS scientists investigate the pathways by which sulfur is incorporated
into fossil fuels.
The forms of sulfur in fossil fuels affect the economics of resource development
and consequences to the environment of fuel use. Specialized laboratory techniques
enable USGS researchers to investigate how sulfur is incorporated into fuels,
from deposition as organic-rich sediment, through burial and maturation. The
isotopic composition of sulfur in different compounds records processes that
affect the abundance and form of sulfur and provides a means for predicting
the occurrence of relatively "clean" fuels.
USGS scientists study the origin and movement of metals and other compounds in ground water.
In some areas, surface and ground waters have been found to contain potentially harmful concentrations of agricultural chemicals or radionuclides such as uranium, radium, and radon. These compounds may be manmade or naturally-occurring, and pose a health risk when present in drinking-water supplies. Integrated studies of the geochemistry, geology, and hydrogeology of contaminated areas help identify specific sources of these compounds and processes that may enhance or retard their movement. As a result of these studies, scientists understand better why some areas are more likely than others to suffer contamination problems. A direct benefit of these studies is that scientists are able to identify methods for mitigating harmful concentrations of these constituents in drinking-water supplies, thus decreasing the public's exposure to harmful chemicals.
USGS scientists conduct research into reactions between rock and water associated with oil and gas production.
Water associated with the production of oil and natural gas from wells commonly
contains high concentrations of dissolved salts. These salts are largely a result
of subsurface water-rock interactions. These reactions can cause changes in
the mineralogy of the rocks hosting the oil and gas, which in turn can modify
fuel accumulation and production. The environmental impact of production waters,
or brines, has economic implications for the development of fuel resources.
To better understand some of these effects, USGS scientists, in collaboration
with the Bureau of
Indian Affairs, have examined brines produced with coalbed methane on
the Wind River Indian Reservation.
USGS investigations of petroleum generation and expulsion yield significant new results.
In terms of hydrocarbon accumulation, the transformation of one particular clay
type to another may be the most significant mineral reaction in the Earth's
crust. Muds containing organic materials and clay are deposited on the sea floor
and eventually covered. As pressure and temperature increase, the original clay
transforms to a more compact form that is better suited to confining conditions.
During this process, water and silica (or other cementing compounds) are expelled.
If petroleum is generated in the mud before the expulsion of fluids, it is carried
into adjacent reservoir rocks by these fluids produced during the clay reactions.
The oil may then accumulate in the reservoir rock, providing a suitable trap
exists. If petroleum is generated after the fluids have been expelled, then
the oil is likely to remain in the shale. Therefore, the relative timing of
petroleum generation and the fluid-expulsion event, resulting from clay-mineral
reactions, is crucial to hydrocarbon migration. A comprehensive understanding
of this geochemical process helps USGS scientists to detail the distribution
of favorable conditions for hydrocarbon accumulation.
E-mail: gbreit@sedproc.cr.usgs.gov