The Environment Effects Of Seismic Exploration

The methods used in the search for oil and gas beneath the seas have come under enormous criticism from environmentalists. In 1999, Greenpeace mounted a challenge to the UK Government under Section 12 of the Habitats Directive. Click below to read the report from the Daily Telegraph:

Government loses battle over Atlantic wildlife - Nov 6, 1999

The ruling confirmed the Habitats Directive application to cover the entire UKCS and not just UK territorial limits. The judge however found against two attempts by Greenpeace to expand the understanding of the Habitats Directive.

While the hazards associated with the dispersal of toxic materials are now well understood, the understanding of the environmental effects that may be associated with noise pollution is in its infancy.

During a seismic survey, strong impulses of waterborne sound are emitted by arrays of airguns which release air at high pressure into the water. The sound returning from the seabed is processed to allow an image of the rock strata and underlying geological structures underneath the seabed to be formed. In addition to the sound that travels downwards into the seabed, the sound from the airguns also travels sideways through the water, and this noise has been cited as causing environmental effects.

Over the past years, Subacoustech has been involved in measuring the noise from seismic surveys in partnership with marine biologists specialising in fish and marine mammal biology.

The North Sea, Wytch Farm and Meldorfer Bucht surveys illustrate the noise propagation from seismic surveys. They have been selected from our data sets to illustrate deep water, coastal water and very shallow water surveys respectively. Click below to see a summary report for each site:

To understand the environmental effects of a seismic survey, a measurement scheme for the data needs to be defined, then the measurements must be analysed according to that scheme, and fitted into a model that enables general conclusions to be made.

Subacoustech's work on audiograms and hearing thresholds (dBht) allows data taken in seismic surveys to be interpreted in a way that represents how the noise is perceived by different species according to their hearing abilities. For example, according to their audiograms, the hearing ranges of fish are within much lower frequencies than marine mammals. Please click on the link below to find out more: