It’s time for the traditional approach to compression design to step aside and recognise the future is subsea.
Not only has subsea compression arrived, it arrives with a ‘warning shot across the bow’ to topsides compression platforms. Designed as they were in the past will accelerate their demise, they must evolve to stop them becoming obsolete. The days when contractors would pull out old designs, change the project title, and “find and replace” the past project name with the new project name are gone. The old adage, “if it ain’t broke, don’t fix it” is simply not valid for topsides any longer. Quicker, faster, stronger, subsea compression is now the benchmark. It’s the Tesla to the established motor industry and just as Tesla proved to the world that electric cars are not only viable but the future of motoring, subsea compression is showing that it, too, is viable and the future of compression.
Subsea compression is no pretender to the throne; it will most definitely have higher value creation than topsides compression and comparing project metrics, will be better in most categories. Why, then, would operators consider an option that has higher HES risk, lower availability, lower recovery for given compression power, higher OPEX and higher CAPEX? Whatever value driver is used, subsea compression invariably comes out on top – yes, even in technology qualification (Åsgard and Gullfaks are both fully qualified at TRL 7). Ormen Lange and Jansz subsea compression projects are testament to the maturity.
The answer to why topsides compression has not yet been retired will likely include politics, outdated perception, lack of knowledge or simply an unwillingness to change. There has been a noticeable shift away from stubborn refusal by operators to those same operators now actively considering subsea compression. But where it isn’t taken forward is most likely due to a difference between what is perceived and what is actual, or to put another way, where a project requirement exceeds the capability of the currently operating subsea compression assets. Simply looking at the specifications for Åsgard or Gullfaks will not tell the full story as this does not take into account the 4+ years of technology development that has continued on since. Where technology hasn’t reached a level required by an operator, the questions to be asked are:
- Is the vendor aware of this requirement?
- Is this a major redesign or (more likely) an enhancement of existing equipment?
- Has the vendor been working on this enhancement anyway?
- As operator, do I need this capability from day one?
Vendors haven’t been sitting idly by waiting for the next big project to come their way; technology is constantly being developed but actual target specifications are much better than best guesses so let the vendors know the requirements. And think about when that capability is actually required: if it isn’t required for a number of years and technology development is manageable, consider a two step approach. Educating decision makers is key to overcoming this barrier.
One of the final challenges that subsea compression needs to overcome is when compression is to be retrofitted on existing facilities where the focus will be the extent of brownfield modifications. In reality, the equipment required is no more than a topsides, and solutions can minimise equipment count on the facility and/or reduce footprint. For example, the Adjustable (Variable) Speed (Frequency) Drives are large units and can take up valuable real estate, but by installing these on the seabed this real estate is returned to the topsides facility.
Just because there is space assigned to future compression doesn’t mean that it must be filled with compression modules! And this appears to be the crux of this particular challenge: an unwillingness to change from an original basis of design, when prior to subsea compression being an option, space has been earmarked for topsides compression and topsides compression it must be. Retrofitting compression topsides will require large gas turbines regardless of whether topsides or subsea is employed and operators and contractors should now be considering replacing direct drive compressors with generators and electric driven compressors – not only does this improve reliability, but also provides flexibility for subsea compression in the future.
For projects already in FEED or where topsides has been selected ahead of subsea, operators and engineering companies alike, need to recognise that any future brownfield addition of compression on that facility will unlikely be topsides. The future designs shouldn’t have direct drive compressors in the frame; generator sets and motor driven compressors should be the starting point and provision for subsea compression written into the Basis of Design. In most cases this provision for subsea compression should be less onerous than topsides modules, particularly if subsea ASDs are deployed.
With the two main compressor technologies in operation since 2015, the suite of enabling technologies qualified this year, and the two subsea compression projects in FEED, the Future is Subsea: long live the King.
To be continued ….