Floating LNG Production Facility

Objective The objective of the study was to prove the feasibility of a floating LNG (FLNG) production facility for the NnwaDoro gas field, to provide solutions for identified problems and to demonstrate that all FLNG related requirements could be met. This paper will mainly focus on the safety and layout aspects of the study, but includes also the other parts of the work performed by Aker Kvaerner Process The study was based on the Linde MFC ® (Mixed Fluid Cascade) LNG Process for the production of 5.8 MTPA LNG plus propane, butanes and condensate in a single process train. The study was performed by Linde and Aker Kværner as subcontractor on behalf of the MOU Team; Statoil, Shell and NNPC. HSE For the NnwaDoro FLNG barge the aspects of gas dispersion and gas explosion was considered as key elements when assessing the governing key parameters for the barge layout. The only established type of method to determine dimensioning explosion loads and gas release type and rate is to perform a proper Risk Analysis, calculating both the probability of accidents to occur and the associated consequences. For a Concept Study this is traditionally performed on a coarse level, however, using all the available information in the project at that time. For the NnwaDoro Study the relevant information available was the Process Flow Diagrams, the 3D model, wind data plus the process calculations. In addition to this generally available information was used. A relevant methodology to be used for a Risk Analysis is NORSOK Z-013. All explosion and dispersion calculations done within this study was sample calculations. It is important not to misinterpret the safety work carried out under this contract as a substitute for a coarse Risk Analysis. However, the gas cloud sizes and ignition points as well as release rates were chosen in order to be conservative. It was our objective to produce a NnwaDoro FLNG design which was robust and able to absorb natural design development during the coming phases without overturning the basic layout. However, the accidental effects calculated were anticipated to be well within the realistic range. In the course of this study the major FLNG related safety issues have been identified, i. e.:Explosion loads within modules and its impact on other SystemsImpact of explosion loads on carrier during side by side LoadingA safety philosophy for the FLNG facility was establishedDispersion studies was performed and the dispersion of gas jet and general ventilation in the process modules was found to be within acceptable limits