Abstract: The initial separation of the fluid provided from an oil well using a separator previously known only from the area of degassing and flotation of process water from oil recovery.

Abstract: In a plant for purifying water contaminated by droplets of hydrocarbonaceous liquid, which plant has an essentially vertically positioned filter (4); an inlet chamber (7) for said contaminated water partially defined by a first vertical surface (5) of said filter; supply means (8) for contaminated water debauching in the lower portion of said inlet chamber (7); and outlet means (9) connected to the upper portion of said inlet chamber (7) for discharging hydrocarbonaceous liquid separated from the water in said inlet chamber; the operational period between filter cleaning and/or the hourly capacity of the filter is increased by injecting fine gas bubbles into the contaminated water at at least one location selected from locations in the lower portion of said inlet chamber (7) and locations in said supply means (8) to produce a stream of gas bubbles upwards along said first vertical filter surface (5).

Abstract: A combined degassing and flotation tank for separation of a water influent containing considerable amounts of oil and gas. A rotational flow is created in the tank which forces the lighter components such as oil and gas droplets towards an inner concentric cylindrical wall where they coalesce and rise to the surface of the liquid and are removed via the outlet. The heavier parts are forced down where the heavy particles sink to the lower part where they can be removed as a sludge. The water is discharged via an outlet in the lower part of the tank. The combined degassing and flotation tank is particular suited for use in oil production at sea for removal of oil and gases from water streams before the water is returned to the sea.