Gas-to-liquids FPSO studied for production processes

• Armstrong Technology's Producer FPSO vessel design continues to be developed for new applications. [19,996 bytes]

Three times the UK's total gas consumption is burned off from oil fields where there is no cost-effective way of getting the associated gas ashore. In response, Armstrong Technology is conducting a study to develop a floating gas production and storage platform, which is being sponsored by the UK Department of Trade and Industry through a partially funded SMART research project.

According to sales and marketing manager Colin Baker, Armstrong wants to be the first British design company to develop this type of platform. "There are gas-to-liquid plants on shore already, but no such processing facilities currently exist on offshore floating platforms," explains Baker.

The study, which currently is in the initial concept phase, combines Armstrong Tech nology's experience in FPSO design and costing with the expertise of specialist gas process engineers in consultancies and uni versities. The outcome of the study will include a cost model which will allow different processes for exploiting natural gas reserves to be evaluated.

Gas production and export processes being considered include:

• A cryogenic plant to produce liquid natural gas for which there is a growing world market
• Trapping the gas in hydrates which can be shipped ashore for subsequent release of the gas
• Translating the natural gas into a liquid which is stable at atmospheric temperatures and pressures.

The cost model will include design algorithms for sizing a platform necessary to support the production plant and to store the LNG, hydrate or liquid products. Platform size considerations also take account of motion requirements for effective operation of the process plant.

While designs for Armstrong's newbuild Producer FPSO series, which has been developed for modular construction, have already been included in three offshore tenders, Armstrong continues to develop the concept further.

For instance, the company is currently evaluating a version of the Producer with the accommodation forward of the turret and dynamic positioning system to suit Norwegian practices. A larger, 2 million bbl version is also being designed to operate in areas such as West Africa.

Away from the FPSO market, Armstrong is diversifying into designing barges for use with tension leg platforms, semisubmersibles and jackup rigs. According to Baker, the complex design would act as a barge for 1-2% of its life, and would then be lifted to act as a process deck. The barges, while generically similar, are designed to individual specifications as each one is supported differently when raised out of the water.

"The advantage of using a barge structure is that it can be brought back to shore to change modules as required," says Baker. "The barge design also allows for rapid fabrication in parallel with the process and accommodation modules, to meet the often early production targets set by oil companies.

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