The transfer of hydrocarbons from subsea wells to a collection point on the sea surface has been accomplished in a variety of different ways. For large deposits of hydrocarbons expensive subsea towers or floating platforms have been used. For smaller deposits whose production does not justify the expense of a subsea tower or floating platform, a surface collection vessel has been used. The surface collection vessel is specially moored to remain at a relatively constant location over the subsea wells. However because of waves, currents and wind, the surface collection vessel will rotate or weathervane around the surface terminus of the production risers. With such rotating or weathervaning motion of the surface collection vessel, it is often difficult to install a reliable system which can accommodate the rotation of the surface collection vessel and still maintain a fluid flow connection with the production risers extending from the subsea wells to the sea surface.
Various complex systems have been proposed to maintain fluid flow connections between a weathervaning vessel and the surface terminus of production risers. Such systems are described in U.K. Patent 2,270,132 and in U.S. Pat. Nos. 4,915,416 and 5,113,778; however, because of the reliability and complexity of those prior art systems, none of these systems has been widely adopted by the industry.
There remains, therefore, a need in the art to provide a simple, reliable system which will allow rotation or weathervaning of the surface collection vessel with respect to the surface terminus of production risers. Such system should not put undue stress on the production risers or create the possibility of leakage of the hydrocarbons as they flow from the production riser into temporary storage on board the surface collection vessel.