ABB Customer World: Powering an offshore platform on the sea bed


HOUSTON -- It’s no secret that upstream oil and gas operators have had to dramatically cut back their investments in recent years due to low crude prices. Prices have improved from their sub-$40 nadir in late 2015, but long-term investment decisions are still challenging. But one area of research and development has continued on even while others were cancelled: subsea technology.

The reason is simple. The industry’s vision for moving topside operations to the sea floor, while a daunting challenge, promises great benefits in higher recovery rates, improved safety, lower costs (both capex and opex) and extended asset life. The “subsea factory” of the future will also enable smaller, more distant fields to be developed economically.

Image: ABB.

Since 2012, ABB has worked with a trio of industry majors—Statoil, Chevron and Total—to bring the subsea vision into reality. At the heart of this project has been overcoming the challenge of powering the pumps, compressors and other equipment to be placed on the seabed.

Today, most of the equipment in an offshore oil and gas system is found topside, but as the figure below shows, in the future almost everything will be moved below the surface. That means that the power to run all that equipment must be sent to the sea floor and distributed among a variety of different loads.

Bringing power to the seabed is not new—ABB delivered the first subsea transformer in 2000 and it remains in operation—but historically the load has been minimal as most of the equipment at depth is passive. Now industry players are looking to move processing equipment to the sea bed, and that means a much greater demand for power and a greater challenge in getting it there.

One of the major issues to date has been that power cables are limited in terms of distance to serve a long step-out, 100 km at most. Also, it’s typical for each load to be served by its own cable. Not surprisingly, then, power cables represent the largest single cost for a typical offshore project.

Now, thanks to advances in power transmission technology, it is possible to drive multiple loads from a single cable and the range of long step-outs is extended to 600 km, so the power supply can reach almost any existing field.

Early projects have already borne fruit. Statoil’s Åsgard gas field, for example, has operated with gas compression on the sea floor for 1.5 years with no disruptions in the power supply. This is impressive when you consider that the equipment must endure 300 bars of pressure and operate within maintenance intervals of five to seven years.

ABB is working now with its industry partners to develop the remaining needed technologies to commercialize the subsea factory concept. The first prototype for a complete subsea solution is currently in testing at ABB’s laboratory in Türgi, Switzerland, and will move on to underwater testing in Finland later this year. There researchers will address the challenge of equipment cooling, less of a challenge in the frigid depths but more so in shallower areas closer to shore where the water is warmer.

ABB anticipates further development and testing of components through next year with pilot projects slated for 2019.

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