US Patent 7152681 Method and arrangement for treatment of fluid

A method utilizes the energy of water that flows out from a high-pressure reservoir. Water and hydrocarbons are separated in a down-hole separator and are brought separately to the seabed. In a first aspect the energy of the water is utilized to inject the water into an underground formation with a lower pressure. In a second aspect the energy is utilized to drive a turbine which in turn is driving a pump for pressurizing hydrocarbons. The invention utilizes a method and an arrangement to control the separator by control valves on the well head for each phase.