The British Petroleum Company, P.l.c.

Intevep, S.a.

David E Graham

David G Thompson

Werner A Lidy

Ignacio A Layrisse

Maria Luisa Chirinos

Mahmood N Mahmood

David E Brown

Alan Stockwell

Malcolm T McKechnie

Maurice C Man

Susan Anderson

Patrick C McGrath

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 crude oil containing residual salt water with wash water of lower salinity than the water present in the crude oil and allowing the resulting mixture to settle into a layer of crude oil of reduced salt water content and a layer of saline water. The quantity of wash water employed is greater than 7.5% by volume of the crude oil. The saline water may be recycled and a proportion removed from the recycle stream and a corresponding quantity of water of lower salinity added. Washing with relatively large quantities of water results in the formation of a less stable emulsion. Consequently, less severe conditions are required to break it to recover the desalted crude oil.

Method for desalting crude oil

Emulsions of oil and water are broken by treating them with a demulsifier which is a polysiloxane polyalkylene oxide copolymer in which the polyalkylene oxide segment is composed of random ethylene oxide and propylene oxide units. The demulsifier is particularly useful in breaking emulsions of water in crude oil which are normally difficult to separate and in breaking emulsions at relatively low temperatures, e.g. 30.degree. to 45.degree. C.

Demulsifying process

The present invention relates to a method of inhibiting the formation of and/or breaking of preformed mercury butter in chlor-alkali cells. The method comprises introducing at any one of the numerous stages of the electrolytic process an aqueous solution of a surfactant material which enables the interfacial tension of the sodium-amalgam interface to be increased to or maintained above a value of 180 dynes/cm. The surfactants may be extracts of decaying vegetation, solutions of carboxylic acids or chlorohydrocarbons. Extracts containing lignite or humic acids are most effective.

Method of inhibiting formation of and breaking of mercury butter in

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Fleet, United Kingdom

David E Graham