Method and equipment for offshore oil production by intermittent gas injection

PCT No. PCT/GB97/01199 Sec. 371 Date May 20, 1999 Sec. 102(e) Date May 20, 1999 PCT Filed May 1, 1997 PCT Pub. No. WO97/47857 PCT Pub. Date Dec. 18, 1997A subsea primary separating vessel (2) is installed close to the wellhead (1) of an oil producing well to effect primary separation of the liquid and gas phases of the produced fluids. A line (3) connected to the top of the separating vessel allows the separated gases to flow to a collecting vessel (7) located at any gathering station. The liquid phase flows to the gathering center through a flow line (21) which distributes the fluids into a U-shaped pipe length (13), each end of which is connected to a flow line (4 or 5) along which the liquid phase flows to a surge tank (8). When the volume of liquid phase which has settled out within the flow lines begins to exert a back pressure which has a prejudicial effect on well production, high pressure gas can be injected into the flow lines for a specific period of time to promote flow of the liquid phase to the surge tank (8). If it is desired to increase the efficiency of the flow, a mechanical interface driven by the high pressure gas may be used to promote removal of the liquid phase.