During the last 5 -10 years the oil and gas industry has shown a growing interest for offshore and nearshore LNG liquefaction and regasification facilities as part of the LNG chain as alternatives to the traditional onshore plants. This is to a large extent driven by safety and environmental aspects as well as the need to find solutions for associated and stranded gas.
This paper primarily focus on the substructure part of such facilities and the LNG containment system. These solutions can be utilised for liquefaction plants as well as for regasification terminals as illustrated on Fig. 1.
Fig. 1 LNG Value Chain - Two offshore LNG facilities possible(AVAILABLE IN FULL PAPER)
Liquefied natural gas (LNG) is the most used method for gas transport over longer distances. A LNG chain starts at the liquefaction plant located nearby the gas production source. The LNG is transported by specialised carriers to receiving terminal(s) for regasification near the market. Developing a base load LNG chain requires an investment of several billion dollars. The need to exploit remote gas reserves is increasingly urgent as well as supplying the clean gas in a safe and environmental friendly way as close as possible to the larger consumer regions.
The use of high quality offshore concrete structures combined with LNG containment systems proven in the marine environment is currently being investigated for a number of applications in Europe, North America, South America, West Africa and South East Asia. The concrete material has well proven material characteristics in relation to cryogenic temperature exposures, high quality concrete used in offshore structures for more than 30 years have shown excellent durability.
Typically, the concrete structure based on a gravity based concrete box for shallow water or a floating concrete barge for deep water, is combined with an internal integrated LNG containment system offering spacious areas at the top of the concrete structure for liquefaction or re-gasification utility and loading facilities. The structures may also offer harbour protection, berthing and mooring arrangements for the LNG carrier. Some concepts are shown in Fig. 2.
Fig. 2 Offshore Concrete solutions for LNG plants and terminals(AVAILABLE IN FULL PAPER)
The facility may be built and completed to the highest degree of completion at a suitable site where infrastructure, manpower and facilities are available or can be arranged. Limited land claim or onshore areas will be exposed during operation and after use the facility can easily be decommissioned and removed for re-use or recycling.
During the last decade concrete offshore platforms have successfully been built in Norway, UK, France, Canada, Australia and the Philippines utilising local labour. Local labour force and engineers as well as local materials and facilities have been used giving a local content of 70% or more.