Buoyant Leg Storage and Regasification Platforms

Summary Environmental loads encountered by offshore compliant structures are more severe in deep water in addition to the complexities that arise during their installation. Because existing platforms show serious limitations in terms of storage space, geometric forms of offshore compliant platforms require special attention. A recent development in offshore deepwater platforms is the buoyant leg storage and regasification platform (BLSRP) to store and process liquefied natural gas (LNG) offshore. One of the main operational requirements of LNG tankers is that the degree of compliancy on the topside should be restrained to a large extent. The conceived structural form is a hybrid concept, which restrains the transfer of both rotational and translational responses from the buoyant legs to the deck and vice versa. The proposed platform consists of a deck connected to six buoyant legs through hinged joints; the buoyant legs are connected to the seabed using taut-mooring tethers. Taut-moored tethers and deep-draft buoyant legs resemble the behavior of a tension leg platform (TLP) and spar platform, respectively. The novelty of the design lies in the deployment of the buoyant legs, which are isolated from the large deck by hinged joints. One of the primary advantages is improved functionality in terms of an increase in the storage and processing facilities for LNG. The deck is connected to each of the buoyant legs with separate hinged joints. Because the buoyant legs are not interconnected, independent movement of the legs does not compromise the high degree of compliance offered by the hinged joints. This chapter presents experimental investigations carried out on a scale model of a BLSRP in the presence of regular waves. Numerical studies carried out on the prototype of the BLSRP with both regular and random waves for different wave approach angles are also discussed in detail. The BLSRP shows desirable responses given both operational and phenomenal sea conditions, ensuring safe operability and incorporating the main advantage of improved functionality in terms of increasing the storage and regasification capacity for LNG. This new-generation geometric form for the offshore compliant platform is prima facie in favor of the design and development of offshore processing and storage of LNG, which will reduce the cost of oil and gas exploration. Studies carried out on the BLSRP model are contributions from R.S. Lognath (2017, “Dynamic Analyses of Buoyant Leg Storage & Regasification Platforms Under Environmental Loads,” PhD thesis submitted to IIT Madras, India) and sincerely acknowledged.