This paper introduces a new concept of Spar platform called S-Spar which is designed accounting for significant features of environmental conditions in South China Sea. First order wave exciting force RAO and motion RAO are captured. Its motion response under internal solitary wave with mooring system is determined. Mooring stiffness is calculated with catenary theory, and wave force exerted by internal solitary wave on Spar platform is estimated with Morison Equation.
The floating structure Spar is recognized as one of the preferred deepwater solutions for the production of oil and gas in the offshore industry. Compared with other floating structures, Spar platforms have excellent stability, motion behavior and adaption to wide range of water depth. On the other perspective, rigid risers and dry tree system are available on Spar platforms. According to those merits, Spar platforms are then regarded as an attractive and economic solution for the development of deepwater. Three types of production Spars have been built to date: the "Classic" and "Truss" Spars, and third generation Cell Spar. With the rapid development of deepwater oil industry, many new technologies and innovative Spar concepts are introduced to adapt to new operation conditions and ultra-deep water depth. So far, Spar concept has been almost exclusively in the Gulf of Mexico, where it has proved a competitive solution for small fields in deep water. Meanwhile, lots of attentions are focused on South China Sea for its rich storage of oil and natural gas. The South China Sea region has been proven that oil reserves estimated at about 7.5billion barrels, and oil production in the region is currently over 1.3 million barrels per day. While, it was also noted (Xu, 2002) that the depth of the basin of the South China Sea is over 3,600 meters and the environment conditions are relatively severe.