#MarineNotice - The latest Marine Notice from the DTTAS concerns the scheduled recommencing of a 3D seismic survey over the Corrib Gas Field by Shell E&P Ireland Ltd.
Some 40% of the survey was completed in 2012, and the remaining 60% is now set to be conducted with a planned starting date of 20 February 2013. Weather permitting, the survey should be completed in June 2013.
The seismic acquisition will comprise a four-boat operation. The M/V Ocean Pearl (Call sign C6ZW4) will lay the ocean-bottom cables on the sea floor and will collect all data records, while the M/V Malene Ostervold (Call sign LCIU3) will serve as the source vessel. In addition to these vessels, a third vessel, the M/V Vikland (Call sign C6UL5) will assist the M/V Ocean Pearl with cable laying and also act as a utility vessel. A fourth vessel, the M/T Deilginis (Call sign EISL), will act as a guard wessel.
Seismic acquisition will occur over a set of four active 12km-long solid ocean-bottom cables laid 400m apart on the sea bed at a depth of 350m. At the end of each cable is a 1km lead-in section which is attached to a standalone buoy at surface. These buoys contain a power pack as well as a recording system. Each buoy contains a radio-link with the cable-laying vessel for remote control of the buoy and for data quality control. Each buoy has a GPS receiver, so its location is well known to both seismic vessels. One by one these cables are 'rolled along' (ie picked up from the northern edge of the active spread, and redeployed at the southern edge). The M/V Malene Ostervold will be towing two seismic sources, and operating around the set of four active 12km-long cables.
The overall survey area is divided into three work areas or Contact Zones (A, B and C). A Contact Zone is defined by a 10km radius circle. Radio Navigation Warnings will be given out daily by the Irish Coast Guard, giving the co-ordinates of the centre point of the Contact Zone for that day. All vessels will be listening on VHF Channel 16 throughout the project.
Full details - including co-ordinates and maps of the survey area - are contained in Marine Notice No 07 of 2013, a PDF of which is available to read or download HERE.