Glossary
Drilling
wastes: are primarily composed of cuttings and muds,
are the most substantial discharge during exploratory drilling.
Drilling mud is used to control subsurface pressures, lubricate
the drill bit, stabilize the well bore, and carry the cuttings
to the surface, among other functions. The compositions of
cuttings is determined by the rock being drilled and often
contain heavy metals such as mercury, lead, cadmium and zinc,
sometimes they contain naturally occurring radioactive materials
as well.
Drilling muds vary in composition but can be either synthetic
based muds, water based muds or oil based muds. Drilling muds
often contain bentonite, barite, biocides, and anticorrosion
agents. While the content of drilling muds and cutting varies,
they are typically saturated with hundreds of different substances
and compounds and according to Russian scientist, Dr. Patin,
their discharge into the sea is one the main ecological threats
during offshore oil production. For more information about
the ecotoxicological effects of the various drilling fluids
check out Patin,
1999.
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Produced waters: are the water which is produced during
the production of hydrocarbons.
Produced waters typically include formation water, brine,
injection water and other technological waters. All of these
waters are usually polluted by oil, inorganic salts, and trace
metals but the composition varies between oil fields and can
be difficult to predict.
Produced waters are one of the main sources of oil pollution
in area of offshore oil and gas production. For example in
the North Sea produced waters are responsible for 20% of all
oil discharged from the oil and gas activity in the region.
The volumes of produced waters created and released into the
ocean increase as an oil field ages.
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Seismic testing: is the
first stage of exploration and is a technique used to locate
potential offshore oil and gas reserves. Seismic testing requires
shooting high pressure sound waves into the ocean that are
directed at the seabed. The activity is thought to be highly
invasive because of the intense noise it introduces in the
marine environment. There are international scientific concerns
regarding the impacts of seismic testing on marine mammals,
fish, and other marine life.
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