This article, written by Technology Editor Dennis Denney, contains highlights of paper OTC 16716, "Hydrodynamic Aspects of Gravity-Based Structures in Shallow Water," by B. Buchner and G.E. Loots, Maritime Research Inst., The Netherlands, and G.Z. Forristall and E.J. van Iperen, Shell Intl. E&P, prepared for the 2004 Offshore Technology Conference, Houston, 3-6 May. Concrete gravity-based structures (GBSs) are being studied for shallow-water oil and gas developments. Three subjects must be considered: wave amplification with respect to deck elevations, the hydrodynamics of liquefied-natural-gas (LNG) carriers moored to GBSs, and wave run-up and possible green water on the deck of the GBS. Introduction A concrete GBS for offshore oil production usually consists of a base caisson supporting several vertical columns, which in turn support a deck containing production facilities. Some of the first were built for deepwater fields in the Norwegian sector of the North Sea. The Troll platform in 303 m water depth remains the tallest object moved over the face of the Earth. Soils in the Norwegian sector were strong enough to support the massive structures, and their mass is sufficient to resist the overturning forces caused by environmental loads. Because the base of a GBS is large, it is easily adapted for oil storage. Production can be stored until a load large enough to fill a tanker is accumulated. Malampaya is a good example of GBS use in shallow water. The Malampaya gas field is in water approximately 820 m deep, but the production is sent by pipeline from the subsea wells to the GBS in 43 m water depth, where it is processed. The dry gas is sent to power plants in the Philippines, and the condensate is stored in the base of the GBS for eventual shipping by tanker. Two GBSs are planned for the Sakhalin II project in the Sea of Okhotsk. In this case, another advantage of this type of structure is exploited: they are able to resist forces from seasonal ice cover and ice movement. Recently, several companies began investigating the possibility of building a GBS as an offshore terminal for importing LNG, as shown in Fig. 1. The structures likely will be rectangular caissons, which also will serve as breakwaters for the LNG tankers. They also will store the LNG and support the regasification equipment.