Well here we are again and time really did fly whilst on leave. My apologies for irregular postings and generally not making a better effort whilst at home. I’m back to sea now and already hooked up to the tow line and carrying out heading control once again for the FPSO Gryphon Alpha.
Last time we were here there was a lot more going on and this job is coming to a close for us shortly but we are still required whilst they finalise and check the work already done. I only recently realised I actually hadn’t talked at all about the FPSO and the work that we are doing up here in the sunny North Sea, this post and possibly one subsequent other will hopefully give you a little insight into this particular job. Once again I will be using excerpts from the fantastic rigmover.com to help explain and show the FPSO side of the operation.
Firstly a little history of Gryphon Alpha the FPSO (Floating Production Storage and Offloading vessel)…
Last year during typical North Sea awful weather; the Gryphon FPSO lost it’s heading and began turning so that the wind battered her sides. She then began rocking and after a short time began moving off her required position. A total powerloss was also recorded for around 30 seconds.
In total these events lasted 10 minutes which may not sound like long but it caused massive damage. Of course the oil and gas wells on the seabed were shutdown immediately. However, in that short time, four of the ten anchors broke and serious damage, was sustained to some of the piping system.
Our current job (in rather loose terms) is to ensure that the FPSO remains on the correct heading whilst other project vessels carry out diving operations to fix the damage using a combination of human divers and remotely operated vehicles (ROVs).
An FPSO is basically designed to turn oil into usable oil and store it on board and they can either be a converted tanker or purpose built for this task. This particular FPSO is 260 metres long, 41 metres wide and capable of storing 540,000 barrels of oil at any one time. Once the oil has been refined onboard it can then be offloaded to a tanker and taken to shore.
So how do we keep the FPSO in position as the dive boats carry out their work?
Well we use a system known as Dynamic Positioning (DP) all the vessels on this job are required to use a type of this system within 500 metres of Gryphon Alpha. It is (again in loose terms) a computer system that has control of the ships propulsion, thrusters, rudders etc. When in use this system very accurately maintains the vessel in one position or wherever the operator, in this case yours truly directs the vessel using the system.
We have onboard a tow wire 90mm in diameter and 1000 metres in length that we use to connect to either the bow or stern of the FPSO. Under the instruction of the Tow Master onboard the FPSO we carefully manoeuvre ourselves into the required position and under the required tension to successfully maintain the heading of the FPSO whilst they turn their thrusters and propulsion off to carry out the work.
At the moment the FPSO is in the process of connecting a complex series of pipes and tubing to the turret which in turn is connected to oil and gas wells on the seabed.
The picture shown below is of our survey screen which shows the FPSO outline in green and ten green lines coming from the centre, these are the anchors and the rest of the lines are the pipeline that the dive/ROV ships will be connecting, 17 in total.
This next picture was taken by rigmover and was taken onboard the FPSO, it is of the turret, the turret has all of the anchor chains connected to it as well as various piping that transport oil to the FPSO, it also injects gas into reservoirs and sends control signals to and from all kinds of equipment connected to the turret.
The turret stays in one position facing the same way so that the many connections do not get entwined but the FPSO can rotate about the turret so that it may always face the wind, a very important function especially in order to prevent damage like that caused in February last year, it also plays an important role in the stability of the vessel.
Since the storm devastated the FPSO the repairs have cost in excess of 1 Billion dollars
Until next time,