Marine seismic surveys
Marine seismic surveys are a safe mapping technique for gathering information about the location and properties of oil or gas that may be present deep below the seabed of a given area during the exploration and production phases of a project.
Sound waves are emitted from a sound source at the back of a seismic vessel and sent below the sea bottom.
As they move through the various geological formations, part of the energy is transmitted down to deeper layers, while the remainder is reflected back up to the surface.
The reflected waves are picked up by a series of sensitive receivers and help create an image of what the subsurface looks like in our targeted survey area.
The seismic data is then analysed.
How is the impact of seismic operations on marine mammals managed?
Respecting nature is one of Shell鈥檚 Powering Progress Strategy goals. We recognise there is a growing urgency to protect biodiversity and we are committed to protecting the environment.A full environmental and social impact assessment is conducted in compliance with both national and international regulatory requirements. Surveys are tailored to each specific area and planned to avoid the most environmentally sensitive times of the year for marine mammals (e.g., times of nesting, breeding or migration). The minimum requirements used for mitigations in all surveys are the .
There鈥檚 an exclusion zone of at least 500 meters around the sound source.
The presence of marine mammals is visually monitored by an independent specialist team before and during the survey.
An underwater sound monitoring system using hydrophones listens for any marine mammal activity not visible from the surface, so that appropriate mitigations can be taken.
Seismic activity only commences if no marine mammal activity is observed within the exclusion zone for a period of 30-60 minutes, depending on water depth.
A 鈥渟oft start鈥� then takes place, where the acoustic source is slowly increased from a very low level, to prevent marine mammals from entering the exclusion zone.
How loud is seismic?
Seismic sound sources are short duration, intermittent and loudest close to the source. Sound drops off quickly in the first few hundred meters around it. This is why we maintain an exclusion zone around the source and make sure it is clear from marine mammals before we start operating.
Seismic sound sources are designed to minimise the sound going into the water at frequencies that interfere with marine mammals communication, navigation or feeding.
Curious to find out more about sound and marine life? Watch these from the International Association of Oil & Gas Producers (IOGP).
Industry view on seismic
According to the , industry experience with marine seismic surveying worldwide, combined with several decades of international scientific research, suggest an extremely low likelihood of harm to marine life from appropriately mitigated seismic surveying.
The Joint Industry Programme was set up under the auspices of the IOGP to conduct an independent that improves understanding of the potential impact of underwater sound on marine life.
