LNG transportation issues are growing as more LNG enters the market. And with floating LNG facilities emerging, the ability to safely offload to another floating structure will be a crucial need. Yonghui Lui, senior research engineer, FMC Sofec, told participants at the Offshore Mechanics and Arctic Engineering conference in Halkidiki, Greece, that moving liquid gas from a floating processing facility to an LNG carrier is a particular concern.
"The transfer system from an LNG facility to an LNG carrier is critical," Liu said. "It is a very complex problem to control the motions between the two vessels."
FMC is tackling this problem through a newly developed duplex yoke mooring system that has already undergone model testing.
According to Liu, Southeast Asia supplies most of the world's LNG, with Indonesia the top provider at 28.6%, followed by Malaysia 14.8%, and Australia 7.3%. The relatively benign offshore environment in these regions provided the basis for FMC's model testing, he said.
The tests employed two proven software programs, according to Liu. The research group carried out diffraction analysis using higher order boundary element method (Hobem) software. The group also included software called Softyoke in its analysis. Liu expressed great faith in the programs, noting that Softyoke was used effectively on CNOOC'sBohai QHD 32-6 FPSO in 2000.
Results of the model testing, which included mooring tests, a wave only test, and connection test, among others, proved the viability of the design, Liu said. There was good agreement between design specifications for heave, pitch, roll, and yaw, he said. "We had a very good match."
Though all analysis methods have drawbacks, Liu explained, he has faith in the model tests FMC carried out. There is always some loss of accuracy, but the loss in this case is not that significant, he said.
The duplex yoke mooring system is not yet working in the field, but Liu believes the system is ready for action.
"It is the only proven technology of its type in the industry," Liu said.