Abstract: An apparatus for offshore production of hydrocarbon fluids is disclosed. The apparatus comprises a base and a buoyant structure secured to said base and connected or adapted to be connected to a subsea well or wells. The key characteristics of the apparatus are that: (A) the apparatus includes storage facility means for fluid(s) received from the subsea well or wells and/or for processed fluid(s) produced by the apparatus; (B) the buoyant structure is tethered to the base by a plurality of flexible tethers; and (C) the buoyant structure comprises (i) a sub-surface housing containing facilities for processing fluids received from the subsea well or wells via said storage facility in said base; and (ii) a column extending upwardly from the housing to a level above the sea surface. The invention also relates to the buoyant structure per se.

Abstract: This application discloses a method of extracting hydrocarbons from a submarine well, which is characterized in that a displacement fluid, e.g. water, is injected under pressure into the submarine well, or into a reservoir connected to the submarine well, from a submerged buoy or from a submerged part of a buoy. Typically, the injection fluid is rawwater. A buoy is also disclosed which comprises an upper section (2) arranged to extend above the sea level; and a lower, submerged section (1), characterized in that the lower, submerged section comprises means for providing a displacement fluid under pressure to an output which is connected or is connectable to a submarine well.