High Temperature Crosslinked Polysulfones Used for Downhole Devices

Abstract

Thermally crosslinked polysulfone may be made from linear polysulfone, such as polyethersulfone, in powder form blended with a powdered inorganic peroxide such as magnesium peroxide or another oxygen source, to form a mixture followed by compression inside a mold. The mixture is cured at a an elevated temperature, for instance above 325° C., for an effective period of time to form a dense object. The object is then boiled in water, optionally under pressure, to remove the salt to give a structure that is open and porous which may be used as a filtration device on a downhole tool for hydrocarbon recovery. If a powdered salt is not used, a thermally crosslinked, solid, void-free polysulfone is made which may be strong and rigid at ambient, surface temperatures, but is an elastomer at elevated downhole temperatures, and is thus suitable for use as a packer or an O-ring.

Description

TECHNICAL FIELD[0001]The present invention relates to a new class of sulfone polymers and their applications such as in filtration devices used in oil and gas wellbores to prevent the production of undesirable solids from the formation, and sealing devices which may be used to seal flow paths to prevent fluid from passing at all. More particularly the invention relates to thermally crosslinked sulfone polymers which are strong and rigid at low temperature below glass transition temperature, which materials are also elastically rubbery at high temperature above glass transition temperature.TECHNICAL BACKGROUND[0002]Sulfone polymers are linear amorphous thermoplastics commercially available from companies such as Solvay Plastics. They are widely used as adhesives, composites, or moldings for use in automobiles, household appliances, and other applications. As linear amorphous thermoplastics, they tend to creep under load especially at elevated temperature. Furthermore, they are sensit...

AI Technical Summary

Benefits of technology

The patent describes a method for making thermally crosslinked polysulfone by heating polysulfone powder in the presence of oxygen and a small amount of magnesium peroxide. The resulting material has uniform crosslinking and good mechanical properties. The method can also involve mixing polysulfone powder with inorganic peroxide powder and a powdered salt. The resulting material can be used as a seal in wellbore tools. The patent also describes a wellbore sealing device made of thermally crosslinked polysulfone.

Problems solved by technology

As linear amorphous thermoplastics, they tend to creep under load especially at elevated temperature.

Furthermore, they are sensitive to various solvents resulting in their limits of applications.

However, these methods require additional chemical reaction steps involving expensive chemicals and solvents.

Furthermore, these methods are limited to those commercially available polysulfones having functional end group such as hydroxyl-ended polyethersulfone.

It is known that polyethersulfone is not as good as other sulfone polymers, such as polyphenylsulfone, in terms of chemical compatibilities.

However, these polymers lack elasticity and they are not desirable to be used as sealing materials.

Perfluoroelastomers such as KALREZ® made by DuPont are very expensive.

Certain grades are claimed to have a maximum continuous service temperature of 327° C. However, this has not been verified in practice in downhole applications at high temperature and high pressure for well life duration.

Some of the perfluoroelastomers tend to have cracks during a sudden drop of pressure.

Problems have been found when attempting to make a molded part: the surface is found to be crosslinked, but the internal portion of the materials is not crosslinked, resulting in non-uniformity within the material.

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