Abstract: Disclosed is a buoyancy device for tensioning an elongate vertical (or quasi vertical) subsea structure at a point below the sea surface, anchored at its bottom. The device comprises as its main buoyancy elements a plurality of hollow elongate objects, and further comprises at least one auxiliary buoyancy element comprising a solid buoyant material. Ideally, the solid buoyant material provides enough uplift to maintain the device afloat should the main buoyancy elements be flooded. A riser apparatus comprising such a buoyancy device is also described.

Abstract: Methods and apparatuses for the production of hydrocarbons from an offshore reservoir are disclosed. The hydrocarbons are produced using at least one spur (or flowline), and at least one riser conduit to transport said hydrocarbons from the seafloor to a point at or near the sea surface, wherein an artificial lift method, such as the injection of a lifting gas, is used to help transport said hydrocarbons from the reservoir to said point at or near the surface, and wherein said artificial lift method is applied to said hydrocarbons at a point along the at least one riser conduit, substantially above said seafloor.