Insulated prestressed conduit string for heated fluids

Claim 1

An improved prestressed conduit string for conducting heated fluids through a well bore, said conduit string being comprised of: a plurality of connected-together conduit sections, each conduit section comprising: an elongated large diameter outer tube positioned around a smaller diameter conductor tube, said outer tube being shorter than said conductor tube and being positioned with respect thereto whereby the ends of said conductor tube extend beyond the ends of said outer tube short equal distances; and bushing means positioned at the ends of said outer tube between said outer tube and said conductor tube, said bushing means being fixedly attached to said outer tube and to said conductor tube whereby said conductor tube is in tension prestress and said outer tube is in compression prestress; said conduit sections being connected together in end-to-end relationship to thereby form said conduit string by connector means, each of said conductor means comprising: annular resilient seal means positioned around axially aligned adjacent extending ends of said conductor tubes and between adjacent bushing means of adjacent conduit sections; and coupling means positioned around said seal means and connected to the outer tubes of said adjacent conduit sections thereby rigidly connecting said conduit sections together and compressing said seal means against the sides of said adjacent extending ends of said conductor tubes and between said bushing means of said conduit sections thereby forming a heat insulated sealed joint between said adjacent conduit sections.