As oil and gas companies extend their presence to remote and ultra-deep waters, one of their main challenges is to maintain environmentally responsible operations while maximizing returns on investment. Just like the shipping industry, stationary floating facilities like FPSOs and other Floating Production Units (FPUs) require an enormous amount of power while in operation.
Det Norske Veritas (DNV) announced today the launch of a new concept called OPera – the Offshore Power system for the new era, which consists of a highly efficient power hub and an electrical transmission system, supplying cleaner power to a network of offshore installations.
Essentially, a high voltage power grid supplied by a floating power station.
The power hub has a gas fired combined cycle power plant that increases power generation efficiency by more than 15%, compared with conventional gas turbines alone. The power generation arrangement reduces CO2 emissions with approximately 40%. By consolidating power generation, the power hub also allows equipment to run at more optimal load. This is a major benefit, as it further reduces fuel consumption and overall emissions. The power hub is fueled by associated gas or parts of the export gas produced.
To give us a bit more background on this concept, we chatted with Sven-Erik Børresen, Senior Consultant, Subsea and Well Systems at DNV North America.
RA: When I think of FPUs that need power, I think of FPUs that might be stationed north of Norway such as Goliat. Can you give me more of a background of what is driving this demand or innovation?
The OPera concept can be detailed in different sizes and adapted to different field developments. With the increasing power demand offshore, particularly from subsea consumers, this concept can serve as a more responsible power supply, reducing emissions. A shared power sources also frees up deck space on the connected installations that can be utilized in a number of ways, to be decided by the stakeholders involved.
The pre-salt areas offshore Brazil is an area with massive investments and tens of new future FPSOs, making a good case for shared power supply as well as other shared resources. This is the case example we have focused on when developing the OPera concept. Having a shared power sources saves a lot of power generation equipment and deck space on the connected FPSOs, to be used e.g. for increased lay down areas, redundant or optimized oil & gas processing equipment, improved safety and more.
Another interesting area is the North Sea developments. In addition to connecting to different platforms, OPera may also be connected to shore and serve as a hub for future offshore grids.
What would this power hub look like, theoretically?
The OPera concept is highly flexible in size and configuration, making it relevant for different types of fields and offshore lay outs.
The modular power arrangement makes possible future scaling up (or down) of capacity to meet the power needs of future installations or escalated power demand of existing connected installations.
Depending on water-depth, different platform and hull-designs can support the power plant. To accommodate the power equipment in ultra-deep water scenarios, like pre-salt Brazil, a semi-submersible platform seems the ideal configuration. For shallow water a fixed structure or barge may be optimal.
How would it be tied in to the FPU?
Transformers step up the voltage before the power is distributed to the connected installations. To ensure supply reliability, installations are connected in a closed loop configuration, providing redundant connections. Depending on distances and power capacity, both Alternating Current (AC) and Direct Current (DC) can be viable options.
For the Brazilian pre-salt case example studied by DNV, the power was transmitted to the installations by 132 kilovolt (kV) AC power cables. This case example utilizes next generation dynamic power cables. DNV is heavily involved with the industry, maturing cable design to overcome the challenges of high tensile loads, dynamic response, fatigue and installation of submarine cables. Several dynamic power cable designs are qualified according to DNV’s recommended practice DNV-RP-A203 Qualification of New Technology. For shallower waters, power cables are not as challenging as this Brazilian case.
Any feedback on the idea from field operators such as Statoil or Petrobras?
The concept is launched externally today, though we have received external input when developing the concept, e.g. on the value of the added deck space on the connected installations.
Operators like Statoil and Petrobras are interested in how hubs can optimize offshore developments. A lot of the technology that goes into the OPera concept is also relevant for other electrification concepts, as electrification from shore.