Development of stranded gas fields - one of the industry's holy grails - in West Africa and Asia could be a step closer following a technical study backed by operators and contractors that concluded a floating production vessel for liquefied natural gas (LNG) is technically possible.
Bouygues Offshore and eight contractor partners recently completed an analysis named Azure Research and Development. The study was carried out as part of the European Union's ongoing energy research effort, Thermie. Azure looked at the viability of building a floating LNG plant and associated transport and receiving facilities. The aim was to address all the technical issues involved and "demonstrate that a fully floating LNG chain, from a gas well to a gas distribution network, is a safe and viable industrial proposal."
Based on the research, the major technical issues have been overcome, said project manager Denis Marchand of Bouygues. "We believe we have proved all the technical points," he said. "We believe that we are ready to undertake a FEED (front-end engineering and design) on a specific case."
One of the biggest issues for the project, he said, was proving the concept's safety. Without that assurance, no offshore operator would contemplate using unproven technology.
Another is the issue of transferring cryogenic liquids at around -257°F (-160°C) in open sea. "We had to demonstrate that we could do it with a system that has been based on cryogenic swivels," Marchand said.
Bouygues claims LNG can be transferred safely in open seas with a tandem-loading configuration, using a boom-to-tanker design with special cryogenic hoses supplied by another of the project participants, FMC Europe.
Azure also had to demonstrate the plant equipment needed for a cryogenic cycle could be marinized. Here, the acceleration of the high volumes of liquid by sea motions had to be overcome.
And the project partners had to prove the storage system could withstand an LNG cargo sloshing around and that a membrane containment system, proposed by Bouygues subsidiary Technigaz and GTT, is adequate.
Concrete and steel hulls have been examined as potential platforms for an LNG production vessel. Bouygues developed the concrete hull concept, and Chantiers de l'Atlantique - the French Atlantic coast shipbuilder - worked on a steel hull option.
Floating LNG terminals and offshore LNG transfer systems have been included as part of the study, and all of the chain's key components have been tested.
M.W. Kellogg has developed two scenarios for a liquefaction barge:
a stand-alone gas field development in Southeast Asia with a capacity of 22 million bbl/year and a "dual mixed refrigeration cycle"; and
a 7.3 million-bbl/year West African facility, with a single process train including a nitrogen expander cycle for liquefaction of associated gas from a deepwater oil field.
Italy's Fincantieri has examined a southern European floating receiving terminal. And the SN Technigaz regasification process was based on submerged combustion vaporizers with a LNG storage capacity of 7 MMcf.
A large-scale model of this device was successfully tested using motion data from basin tests. And Bureau Véritas and Registro Italiano Navale supervised a safety assessment of the floating LNG chain's various facilities. Engineering practices from the offshore industry and those for onshore LNG terminals can be combined to meet safety criteria, the partners believe.
Satisfied that all the study parameters have been met, the research partners are looking for a project on which to try out the complete package.
"Now we need to let people know about our work and convince oil and gas operators that they can think of this kind of technology in their development planning for their fields," Marchand said. The work now is the dissemination of the (study) results and convincing people it is viable."
Several papers have been prepared on the Azure project, completed in October 2000 for US $6.04 million. The European Union provided 30% of the cost. The rest came from the contractors and operators who took part in the research.
It is interesting that West Africa and Southeast Asia were chosen as development location scenarios, since in the absence of extensive infrastructure, these are exactly the areas in which this kind of technology could bring energy to those that need it.
"There are possibilities for associated gas in deepwater fields," Marchand said. "Or West Africa could be a candidate."
Conceivably, the same kind of technology could benefit stranded gas reserves in Europe, including the Torridon/Victory field and others west of the Shetland Islands, as well as the southern Mediterranean.
A floating LNG plant could be built within 4 years, Marchand said, and a receiving terminal within 3.
Are there any takers out there?