Importance

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Abstract

A composite drill pipe has a fiber reinforced synthetic tube with a leading end and a trailing end spaced axially from the leading end, with the leading end of the tube being engageable with a bit for drilling a bore through the earth when a force is applied to the trailing end of the tube. Hardened steel fittings are attached to the opposite tube ends and have interengageable threaded portions for joining a plurality of serially arranged drill pipes and forming a flexible drilling string of desired length. Radial holes are drilled around the circumference of the tube ends and into the steel fittings, and stainless steel dowel pins are press fit into the holes to provide a mechanical lock between the composite tube and the fittings. A steel sleeve is placed over the is bonded to the outer surface of the tube. A series of steel-encased centralizer buildups are spaced along the length of the composite tube to align the tube within the well bore and to prevent contact between the tube exterior and the sidewalls of the bore when the tube is advanced therethrough.

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First Claim