RE: The MV Investigator16 Jan 2020 16:57
Salinity and speed of sound tests on site first off to calibrate equipment, I’d have thought the survey would entail a magnetometer, side scan sonar, and if they were going to drill for core samples a USBL for positioning, perhaps one of these items isn’t interfacing correctly, compromised cables of fittings usually, so perhaps they’ve rendezvous for equipment.
Site survey is undertaken for the following reasons:
• To identify any sub surface objects which would damage the instillation of an underwater structure.
• To identify shallow gas areas (pockets) prior to the drill rig entry, jack-up legs being lowered. ( potential for jack-up toppling over negated.
•Investigate slope stability. (Sea bed is rarely completely flat)
• locate seabed cables pipelines
A site specific survey for a production platform must cover an area of 1000m radius, or 100m past anchors (spud cans relates more to semi submersible rigs, so later for us) the spacing for acquiring the seismic data can’t be any greater than 150m, so the survey vessel will go up and down in straight lines, much akin to mowing a lawn, and indeed its affectionately known as such in the industry.
The second ship may have been doing an environmental survey, just a thought, these are also required now.
So you see the site survey won’t just be one piece of equipment but several, perhaps a boomer too for deep penetration of the seabed (upto 50m ish from memory)
But many reasons why she’s returned, from weather to staff sickness, to a football match the crew refuse to miss. (Yep that’s actually happened on a boat I was on once)