Oil and Natural Gas - Energy Policy Analysis: A Conceptual Framework - page 75

Figure 4.1 The Oil and Gas Fuel Cycle

Exploration Production Processing

Waste disposal Combustion Transportation

contain several volatile organic compounds, including methane. Natural gas is mostly methane,
and coal bed methane is an economically recoverable resource in some areas of the United States.
If these resources are to be developed in an economically efficient manner, the oil and gas must
be developed before the coal is mined or significant portions of economically recoverable gas
reserves may be lost.
Exploration for oil and natural gas is similar to that for coal in the United States (see Chapter
2 in this volume), but often includes remote sensing from aircraft to identify geologic structures,
and geophysical seismic surveying to detect the differential in return of high-intensity acoustic
signals through solid material from masses of liquid and gas. Because oil and gas are considerably
less dense than surrounding rock, sound waves reflect back in distinctive patterns that reveal the
presence of such resources. Although the equipment varies, with heavy truck equipment on land
and ships on water, similar technologies are used to explore onshore and offshore resources.
Earlier use of explosives to generate high-intensity acoustic signals produced some destruction
of marine life, but current electronic technologies are thought to be safe for fish and invertebrates,
although there continue to be some concerns about the effects of seismic surveying on marine
mammals, especially whales and others that communicate with acoustic signals (Neff, Rabalais,
and Boesch 1987, 150).
Following a search of available records and geophysical surveying, core drilling and logging of
boreholes determine the amounts of oil and gas that are extractable at specified depths and costs.
On land this may involve building roads in roadless areas for transportation of drilling rigs similar
to those used for coal and uranium prospecting, but offshore it involves mobile drilling rigs on
barges, drill ships, and semisubmersibles fabricated at coastal or inland shipyards.

OFFSHORE RESOURCES

Crude oil seeps naturally into the marine environment, establishing a contaminant “background”
that must be estimated in order to determine the extent of pollution from human activities. This
background rate of natural seepage of crude oil has been estimated at 58.8 to 588 million gallons
per year globally (NRC 2003, 67-69). Activities associated with oil and gas exploration or produc-
tion introduce an estimated 11 million gallons of oil to the seas worldwide each year, including
about 880,000 gallons to North American waters (2). Releases from oil and gas extraction include
accidental spills of crude oil from blowouts of drilling rigs, surface spills of crude from platforms,
and slower chronic releases associated with disposal of produced water and oil-bearing cuttings
created during the drilling process. Volatile organic compounds are commonly associated with or