Understanding Offshore Survey Jobs (Part 1)
Hi everyone! I’d like to talk about the job itself and some facts about Survey Operations. We all know that the wind farm sector is currently more popular than oil and gas. Let’s discuss some interesting topics, as you will decide at the conclusion of the discussion. First of all, what you need to know about Survey Operations? This job is performed before any constructions at sea, to find out seabed state, any UXO on the bottom etc. It can be government order to check blurring of sand close to port, or it can be serious UXO searching before construction of the windfarm.
Before I started working in survey, I had expertise with ROV operations. Comparably to those operations, survey is completely different. However, for some reason I found this job acceptable for me. At the same time, this is a significant problem for individuals who want to work in DP consoles because the DP system is only in use for brief periods of the processing – SVP (Sound Velocity Profile) deployment etc.
My experience started in dry dock. Our client installed special equipment on board our vessel. Let me share with you some specific staff to be used during projects on board survey vessels.
Almost everyone who has worked on DP vessels in the past has probably been in touch with over-side pole (USBL Pole / HPR Pole); therefore. On the lower portion, sensors have been fitted. We installed a Multi-beam (Plate) sensor for the first time along with an additional sensor that was the same as the HPR we already had on board (Red-Yellow). These sensors have been in use throughout all activities together with additional bottom-up data coverage and scanning equipment positioning on operational screens.
The overside pole is prepared for connection. We needed two weeks of dry docking for us to finish all the jobs, and in the end, we needed a few extra days to set up the equipment. Don’t forget about equipment-based sea trials for sure. However, we will discuss that in a moment.
The mobilization’s main phase is still ongoing, so we began by loading the equipment specifically winches. Three winches and one drum are used on board our ship for seismic equipment.
Additionally, we had to wait for the spreader bar to be manufactured at Drydock and then put it on the A-Frame because it wasn't already installed on our A-Frame.
The spreader bar is mounted and all of the sheaves are prepared for usage in the image above.
Equipment recovery from the water is done using a tugger-winch, which is remotely controlled from a controller on the back deck.
Sheaves, the Tugger winch, and the spreader bar pad eyes all underwent load testing after installation was complete. All of the installed equipment has received BV-Class approval.
You can see from the image that the test using the water bag weight was successful.
Above, you can see how the configuration was built and the deck as seen from the stern. and the spreader-bar has sheaves mounted.
Each sheaf has undergone testing and inspection by a third party. Remember to verify all of the shackles and wires used for the project as part of the lifting-gear examination.
Seismic equipment on board, as I've already mentioned. To enable the deployment of gear from the side of the vessel, a unique boom arm was constructed for these tasks. Although not difficult, that construction needed some time to create and install. I'll spare you the details and just show you a picture.
This Boom-Arm was ultimately extended because the initial attempt to deploy it failed. On the end, only a minor addition has been welded. The initial total length of 5 meters increased to 7 meters.
Special parts have been added to the overside pole to lessen water sway. After a few tries, the HPR beacon changed, as seen in the image above. Clear data presentation and the absence of outside disruptions are crucial for survey work. Weather and vessel characteristics play a significant role in this task. For instance, in order to reduce noise during seismic operations, we used one azi-thruster. Throughout the entire project and data processing, special tests were conducted. Finding solutions that will please the client was quite difficult, but in the end, the data was good, therefore we succeeded.
Author: Bogdan Oliinyk
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- DP