Source array modelling, Southern Ionian Sea

Petroceltic proposed to undertake a 3D seismic survey in the Southern Ionian Sea.  The survey area is located approximately 15 nautical miles offshore of Leuca, Italy in water depths from approximately 200 to 900m.

RPS was commissioned to undertake a two-phase study to:

  • Carry out source array modelling and selection study to identify source arrays that would be best suited to the requirements of the seismic survey
  • Carry out underwater propagation modelling to predict the likely range of effects for the proposed source arrays on marine life, including marine mammals and turtles

The results of the study were used to select the source array configuration that would minimise the potential effects of underwater sound on marine life during the survey.

Key details

Project name
Source array modelling, Southern Ionian Sea

Client
Petroceltic

Location
Offshore Italy

Services provided

  • Underwater acoustics
  • Seismic operations management and support
  • Seismic survey design
  • Marine biology
  • Modelling

Challenge

Sound is readily transmitted underwater and there is potential for sound emissions from seismic surveys to affect marine mammals and turtles. At long ranges, the introduction of additional sound could potentially cause short-term behavioural changes, for example to the ability of cetaceans to communicate and to determine the presence of predators, food, underwater features and obstructions. At close range, and with high sound source levels, permanent or temporary hearing damage may occur; extending to possible gross physical trauma at very close range. 

The selection of an appropriate source array for seismic surveys is complex and must take into account various factors such as the physical requirements for obtaining data, which can then be balanced against potential environmental impacts. However, each source array has complex characteristics such as directivity patterns which mean it is difficult to take sound propagation effects into account during the source selection process.

Source array modelling petroceltic - project image.png

Solution

Due to the various interacting and complex requirements of the survey (i.e. to balance source technical requirements against environmental performance), RPS developed a two-phase approach. This involved modelling a number of source array configurations to meet the requirements of the survey combined with propagation modelling to assess the environmental impact.

This allowed the operator to select the most appropriate configuration for the survey whilst at the same time demonstrating to regulators that they have taken steps to minimise the potential impacts of the survey on marine life. A detailed mitigation strategy was then developed to minimise any residual effects from the survey.

Project statistics

3
source arrays taken forward for detailed modelling
200m to 900m
Survey water depths
15
nautical miles offshore of Leuca, Italy

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