Abstract: A spar platform is disclosed having a deck supported by a buoyant tank assembly having a first buoyant section connected to the deck and defining a central moonpool and a second buoyant section disposed beneath and axially vertically aligned with the first buoyant section. A buoyant section spacing structure connects the first and second buoyant sections in a manner providing a horizontally extending vertical gap therebetween and a counterweight spacing structure connects the counterweight to the buoyant tank assembly. A flexjoint receptacle connected to the exterior base of the second buoyant section receives a receptacle connection on the exterior of the riser to support a catenary section of the riser between the receptacle connection and the seafloor. An exterior section of the riser mounts to the exterior of the second buoyant section and an ingress section passes through the horizontally extending vertical gap to the moonpool.

Abstract: A spar platform is disclosed having a deck, a buoyant tank assembly supporting the deck, and a counterweight. A counterweight spacing structure connects the counterweight to the buoyant tank assembly. The buoyant tank assembly has a first buoyant section connected to the deck and a second buoyant section disposed beneath and axially vertically aligned with the first buoyant section. The second buoyant section has a substatially larger diameter than the first buoyant section and a buoyant section spacing structure connects the first and second buoyant sections in a manner providing a horizontally extending vertical gap therebetween. Another aspect of the invention is a method for reducing VIV in spar platform by providing a substantially open horizontally extending vertical gap in the cylindrical buoyant tank assembly between a first buoyant section and a second buoyant section.

Abstract: A deepwater riser assembly is disclosed for a riser connecting subsea equipment to a surface wellhead. A buoyancy can assembly provides an open ended buoyancy can tube which surrounds the upper end of the riser and an upper seal which effectively closes the annulus between the riser and the buoyancy can tube. A load transfer connection in the buoyancy can assembly then connects the riser to buoyancy can tube. A pressure charging system communicates with the annulus between the riser and the buoyancy can tube below the upper seal. Injecting gas into this annulus then provides support to the riser.