Abstract: A fluid treatment tank for use in a well fluid processing system. The tank is divided into at least three compartments, including an oil treatment compartment for receiving oil from a separator vessel of the well fluid processing system so as to allow stabilization and/or final separation and treatment of the oil, a reject treatment compartment for receiving reject fluid from one or more water treatment units of the well fluid processing system so as to allow gravitational separation of heavier and lighter components of the reject fluid, and a water treatment compartment for receiving de-oiled water from one or more water treatment units of the well fluid processing system so as to allow degassing and/or final separation of the water. Also, a well fluid processing system including such a fluid treatment tank.

Abstract: The invention relates to a system for separating oil/water/gas from a marginal field by using a combination of a coarse separator with short treatment duration which separates into three flows where one obtains an oil concentration of over 70%, a water concentration of over 70% and a gas quality for burning off, where the oil and water flows are treated in cyclone systems having defined geometric proportions and a gas portion is reinjected into the water injection flows without the use of a compressor. Gas/liquid cyclones may also be used before the choke valve so that the gas pressure is kept, or optionally reinjected or used for injector pump operation of low pressure wells.