Download May 1997 - The Skeptic Tank

May 1997
MEDIA BRIEFING NOTES
SEISMIC EXPLORATION
What is seismic exploration?
Seismic exploration refers to geophysical exploration for oil and gas by acoustic means. Sound
energy is released near the ocean surface and then reflected back from the seabed at different
levels by different types of rock formation. In the past high explosives were commonly used as
energy (sound) sources, however, arrays of airguns or gas `exploders' are now the dominant
modes. By measuring the reflective sound, survey companies gain information as to the possible
presence of oil and gas reserves beneath the sea bed.
Marine seismic exploration involves a ship towing a source, such as an airgun,
approximately 300 meters behind the ship. Behind the airguns streamers containing
hydrophones receive the sound reflected by the rocks beneath the sea bed. On the Atlantic
Frontier, seismic vessels using up to eight streamers of around five kilometers long are towed at
a depth of approximately five metres beneath the surface.
When used in water, seismic exploration can produce sounds with overall source levels of up to
250 Decibels. Much of the seismic energy is directed downwards, however there is also
considerable seismic energy directed horizontally. Underwater sound pulses from airgun arrays
and similar sources are often audible many tens of kilometers away. Seismic ships will avoid
each other by 50 miles to ensure `competing' sound does not interfere with other seismic
operations.
Implications of seismic exploration on the Atlantic Frontier
Seismic exploration is the first stage of oil and gas exploitation in an ocean area (the industry
refers to such areas as ocean `acreage'). The proliferation of seismic exploration and exploratory
drilling indicates oil industry and Government intentions to expand into the Atlantic Frontier. If
oil resources are identified, full scale industrialisation of this largely untouched oceanic
wilderness will proceed.
The development of the Atlantic Frontier heralds a potentially massive expansion of oil
exploitation as the industry begins to tap previously unattainable resources of oil from the deep
sea as a result of new technology. This development comes at a time when such bodies as the
European Union are calling for urgent action to significantly cut Carbon Dioxide (CO2)
emissions in order to protect the climate. The burning of fossil fuels is the largest contributor to
human induced climate change.
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In order to effectively deal with the urgent need to drastically cut CO2 emissions an orderly phase
out of fossil fuel use is now the only prudent option. In Greenpeace’s
opinion the natural corollary to this is that we do not now develop new frontier oil resources, or
encourage the proliferation of the technology to extract such resources from these deep ocean
frontiers
Illegal licensing of the Atlantic Frontier
Greenpeace, the Whale and Dolphin Conservation Society (WDCS) and the Marine
Conservation Society, with the support of the Royal Society for the Protection of Birds, have
made a formal complaint to the European Commission (EC) about the UK Government’s failure
to implement the EC's Environmental Impact Assessment (EIA) Directive (85/337) for offshore
oil and gas exploration. The lack of such legislation means there has been no formal legal
requirement for Atlantic Frontier oil companies to assess or report the environmental effects of
their offshore activities to the public or Government.
The complaint claims that the recent granting of licenses for offshore oil exploration and
production to oil companies on the Atlantic Frontier are illegal. Licenses have been granted by
UK authorities without regard for the environmental, social or economic impacts of these
activities, including impacts of seismic testing and drilling on wildlife and marine ecosystems
and without any consultation with the general public.
Of particular concern to Greenpeace is the failure of Atlantic Frontier oil companies to
identify and assess the impact of their activities on the climate as required by the EIA
directive.
Seismic work on the Atlantic Frontier
On the Atlantic Frontier, speculative seismic exploration has already been carried out.
This work informed the oil industry of the best possible acreage for exploration and
these areas were identified by the Government as tranches open to bids in the 17th round of
offshore licensing. This exploratory process continues following the awarding of these oil
exploration licenses, and successful oil companies will be contracting for targeted seismic
exploration in their recently granted `tranches'.
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Effects of seismic exploration on marine mammals and fish
A number of studies have raised worries over the effects of seismic exploration
on marine mammals. The WDCS have recently initiated a `statement of concern' signed by
international cetacean experts expressing concern about the effects of seismic exploration on
marine mammals.
Increased oil and gas exploration on the Atlantic Frontier will increase noise
levels from both seismic exploration and increased shipping activity.
A review by Richardson and Malme (1993) on behavioural responses of bowhead
whales to human-made noise concluded that research from a number of studies collectively
showed that when an operating seismic vessel approaches within a few kilometers, most
bowheads exhibited strong avoidance and specific changes in surfacing, respiration and dive
patterns.
Experiments on gray whales migrating along the Californian coast showed reactions to
strong airgun pulses (Malme et al 1983;84). Richardson et al (1995) concluded that in bowhead
and gray whales strong avoidance occurred when received levels are 150-180 Decibels, as occurs
several kilometers from an airgun array. Sperm whales in the Gulf of Mexico have been seen to
move 50 kilometers to avoid seismic exploration, and in the Indian Ocean, sperm and pilot
whales stopped calling when seismic exploration started some 300 kilometers away. Studies off
Pembrokeshire and Cardigan Bay in Wales also suggested an avoidance reaction by common
dolphins to air gun emissions (Goold J. 1996).
All of this should come as no surprise as the world which marine mammals inhabit
is a dark and auditory one. From catching prey to communicating with relations, marine
mammals are absolutely dependent on sound and hearing as their principle mode of receiving
and passing information through the world around them.
In addition to specific effects of seismic exploration, industrialisation of the Atlantic Frontier by
the oil industry will also increase other forms of noise disturbance.
Concern has been expressed since the 1970s that rising levels of human-made
noise may be impairing the natural ability of the larger baleen whales, such as blue whales and
fin whales, to communicate across long distances using low frequencies. This "masking" is
known to occur with fin whales and minke whales in the North American Saint Lawrence
Estuary. It may affect the northern bottlenose whale off Nova Scotia.
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Fish have also been shown to be effected by seismic exploration. Engas (1993) showed that
seismic shooting with airguns has an effect on fish distribution and catching rates for cod and
haddock, not only locally where the shooting takes place, but also in the surrounding area. The
reduction was largest within five nautical miles from the centre of the shooting area, with catch
rates being reduced by between 45% and 70% compared to levels before shooting began. No
increase in fish quantity was observed in the area during the subsequent five days in which the
trials continued.
REFERENCES
Engas, Lokkeborg,s. and Soldal,A.V. (1993). Effects of seismic shooting on catch availability
of cod and haddock. Institute of Marine Research, Norway, Fisken og
Havet, 9,117p
Richardson, W,J., and Malme, C.I. (1993). Man made noise and behavioural responses. In:
Bruns,J.J., Montague, J.J. and Cowles, C.J. (eds) The Bowhead Whale. Spec.Publ. 2, Soc Mar.
Mamm., Lawrence, KS, pp. 631-700.
Richardson, W.J., Greene, C.R., Malme. C.I. and Thomson D.H. (1995) Marine
Mammals and Noise. Academic Press, San Diego, California. Chapters 9-13.
Evan P. and Nice H.(1997). Review of the effects of underwater sound generated
by seismic surveys on cetaceans. Sea Watch Foundation, Oxford.
Goold J. 1996. Acoustic Assessment of Populations of Common Dolphin Delphinus
Delphis in Conjunction with Seismic Surveying. J. mar.biol.ass. U.K. (1996), 76,811-820.
For further information please contact the Greenpeace Press Office on
0171-865 8255/6/7/8 or 0171-359 4837