초록

A centraliser primarily for use when casing an oil or gas well, the centraliser having low frictions coatings or sliders on the outer surface thereof.

대표청구항 ▼

1. A casing centraliser for use in a wellbore having a body with a bore therethrough for receiving a tubular to be centralised, the body having at least one low friction slider on the outer surface thereof, wherein the at least one slider provides a bearing surface with a lower coefficient of fricti

1. A casing centraliser for use in a wellbore having a body with a bore therethrough for receiving a tubular to be centralised, the body having at least one low friction slider on the outer surface thereof, wherein the at least one slider provides a bearing surface with a lower coefficient of friction than the rest of the casing centraliser, wherein the at least one slider comprises any of a button, a patch, a strip, a block, or a blade that is coupled to the outer surface of the centraliser such that the at least one slider contacts the wellbore surface prior to the centraliser contacting the wellbore surface. 2. A casing centraliser as claimed in claim 1, wherein the at least one slider bears against the interior surface of a bore in which the casing centraliser is placed and wherein the at least one slider comprises at least a part of a blade. 3. A casing centralisor as claimed in claim 2, having more than one blade, and wherein the blades are arranged in a peripheral array circumferentially distributed around the body to define a flow path between each circumferentially adjacent pair of blades. 4. A casing centraliser as claimed in claim 2, wherein the radially outer edge of at least one blade has at least one low friction slider in a form selected from the group consisting of coatings, strips and blocks, applied thereto. 5. A casing centraliser as claimed in claim 2, wherein the at least one blade is coated with a low friction material. 6. A casing centraliser as claimed in claim 1, wherein the inner surface of the casing centraliser also has at least one low friction slider in a form selected from the group consisting of blocks, coatings and strips, applied thereto. 7. A casing centreliser as claimed in claim 1, wherein the body of the casing centraliser comprises at least one of the group consisting of Zinc, Aluminum, Steel and a composite material. 8. A casing centraliser as claimed in claim 1, wherein the at least one slider engages in an aperture in the body, so that the slider protrudes slightly from the aperture to extend slightly proud of the outermost surface of the casing centraliser body. 9. A casing centraliser as claimed in claim 1, having more than one slider, wherein at least some of the sliders are of a form selected from the group consisting of buttons, patches and strips that are coupled to the outer surface of the body, so that in use they will contact the interior surface of a bore in which the casing centraliser is placed before the rest of the body of the casing centraliser. 10. A casing centraliser as claimed in claim 1, wherein at least a portion of the at least one slider is formed from compounds selected from the group consisting of: engineering plastics; polymeric ethylene compounds; nylon compounds; Polytetrafluoroethylene (PTFE); polyetheretherketone; carbon reinforced polyetheretherketone; polyphthalamide; polyvinylidene fluoride; polyphenylylene sulphide; polyetherimide; polyethylene; polysulphone; polyethersulphone; polybutyleneterephthalate; polyetherketoneketone; polyamides; phenolic resins or compounds; thermosetting plastics; thermoplastic elastomers; thermoplastic compounds; thermoplastic polyester resins; Polyethlene Terephthalate (PETP); and chemical equivalents and related compounds. 11. A casing centraliser as claimed in claim 1, wherein the at least one slider is not, of even depth. 12. A casing centraliser as claimed in claim 1, having more than one slider and wherein at least one slider differs from the others. 13. A casing centraliser as claimed in claim 1, wherein the body has a low friction coating and the inner and outer surfaces of the body are at least partially coated with one of the group consisting of PTFE-impregnated nickel and phosphorous. 14. A casing centraliser as claimed in claim 1, wherein the body has a low friction coating of uneven depth. 15. A casing centraliser as claimed in claim 1, having at least one blade, and wherein the at least one slider engages in an aperture in the at least one blade, so that the slider provides slightly from the aperture to extend slightly proud of the outermost surface of the blade. 16. A casing centraliser as claimed in claim 1, having at least one blade and having more than one slider, wherein at least some of the sliders are of a form selected from the group consisting of buttons, patches and strips that are coupled to the outer surface of the at least one blade, so that in use they will contact the interior surface of a bore in which the casing centraliser is placed before the rest of the casing centraliser. 17. A casing centraliser for use in a wellbore having opposing surfaces, the centraliser having a body with a bore therethrough for receiving a tubular to be centralised; the body having at least one blade; the blade having at least one low friction slider provided its outer surface; and wherein the at least one slider provides a bearing surface with a lower coefficient of friction than the rest of the centraliser; wherein the blade is coupled to the outer surface of the centralizer such that the slider contacts the wellbore surface prior to the centraliser contacting the wellbore surface.