RAM in (De)Manning Studies
Christopher Cooper
"They say Rome wasn't built in a day, but I wasn't on that particular job"
General
As part of COMPANY’s drive towards improved safety, efficiency and reliability the development was being considered to be operated as an unmanned installation. The field was remote, in a harsh environment in the Norwegian Sea at a water depth of approximately 1300 m and 300 km from shore. The study was performed in parallel with other field development work based on a manned development.
As a basis for the study the process scheme and equipment list from the manned investigation was provided for the minimum process case. In close cooperation with COMPANY the following main scenarios have been defined and considered as potential concepts for a zero to low manned installation:
· Normally Unattended Installation (NUI), no overnight stays
· Not Normally Manned Installation (NNMI), overnight stays allowed
· Minimum Manned Installation (MMI), continuous manning
· Low Manned Installation (LMI), continuous manning
To assist the estimate of maintenance levels COMPANY provided comprehensive maintenance data for two other fields and also provided operational input on a regular basis.
The conclusion from the study is that the facility can be operated in an unmanned mode safely, efficiently and reliably.
The topside weight and the substructure were significantly reduced compared with a manned installation. The CAPEX has a saving potential in the range of between 25 to 30% and the yearly maintenance manhours will be in the range of 9000 to 10000 manhours for the topsides with an additional 1000 to 1500 for the marine systems.
Availability
A coarse availability model was constructed in order to compare options and to obtain an estimate of the likely availability that could be achieved.
The table below shows the results of the availability calculations. The first row shows the results without considering weather outages or export line pack. The second row shows weather effects only, the third row shows weather effects plus line pack based on a 26” export line and the fourth row is the same but with a 36” export line.
The results for the NUI and the NNMI are very close to each other. In fact the small differences do not show until the 2nd decimal place. This is because the process is the same for both and the only differences that have an effect on availability are the presence of a firewater system on the NNMI and slightly different mean times to access due to the fact that no overnight stays are allowed on the NUI.
It was a very interesting project and a great way of incorporating RAM in a wider study. It’s also another illustration of utilising actual failure data to give a better insight. The high availability achievable without manning showed even 10 years ago that demanning was a potential option. Now with new technology and better reliability it does seem that more and more fields will be considering this given the obvious CAPEX and OPEX reductions it can also provide.
Reliability Leadership - Asset Management, RAM(S) Engineering, Maintenance, RCM / FMECA, ERP/EAM, Reliability, FTA, RCFA. KTP Supervision.
4yVery keen to echo the need for performing RAM modelling and analysis at the earliest possible project stages.
Operations Director at Hydraulic Analysis Limited
4yHi Chris. I was always impressed with the level of detail that was assessed when considering demanning a platform. We have done a few studies on firewater systems whereby the entire piping system, including the ringman was kept fully drained when the platform was demanned. Prior to a visit, the firewater system was remotely activated and re-primed. It was very challenging ensuring the ringman was refilled stably in a controlled manner, especially controlling when and where the two water slugs met at the far side of the ringman and the last bit of air was vented. We needed to model this accurately so a dump line could be installed at this location to ensure there was no air lock present. We did some very clever updates to our surge analysis software to model the air pressurisation and venting with water travelling from two different directions. Was a great project to get involved with and I learnt a lot!
I HELP UPSTREAM OIL AND GAS COMPANIES WITH EFFECTIVE ENGINEERING STRATEGY: ENGINEERING MANAGER: PROJECT MANAGEMENT:
4yGreat analysis. Was wondering did the equipment on the platform did have some rotating equipment??. Or was it minimum facilities with no compression.