The British Petroleum Company, P.l.c.

Malcolm T McKechnie

David G Thompson

Gareth Charles Jeffrey

David E Graham

David L Perry

A method for reducing the tendency of a surface of a material to foul when exposed to a potential foulant comprises the step of treating the surface of the material with a plasma of a compound containing or generating hydroxyl groups to render the surface hydrophylic but substantially uncharged. The materials may be inorganic, e.g. glass, or organic, e.g. polyamide, and may be in the form of fibers, woven fabrics, membranes or plates. Suitable compounds containing hydroxyl groups include ethylene glycol and water.

Method for reducing fouling

A backwashable filter element consists essentially of a fabric of polyacrylonitrile fibres wherein the diameter of the fibres is in the range 10 to 50 microns and the density of the element is in the range 0.05 to 0.50 g/cc. The element is suitable for use in filtering sea water, particularly for sea water injected into petroleum reservoirs to assist in the recovery of crude oil.

Equipment and method for filtration using a fabric of polyacrylonitrile

The salt content of crude oil is reduced by washing it with at least 1% by volume of wash water of lower salinity than the water present in the crude oil and separating the resulting mixture of oil and water into a layer of crude oil of reduced salt content and a layer of saline water containing some oil. The latter is passed through a cross-flow membrane separator and the oil-free permeate is removed from the separator as effluent. The oil retentate is recycled from the separator to the washing stage and a quantity of lower salinity than the water associated initially with the crude oil is added to the washing stage. The quantity of added water corresponds at least to the volume of permeate removed from the cross-flow membrane separator. Since the oil is recycled, the need for oil recovery plant for treating desalter effluent is removed.

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Egham, United Kingdom

Malcolm T McKechnie