Retrievable bushing for well conduit

Claim 1

A retreivable bushing for insertion in a well conduit comprising: an outer tubular assembly insertable in series relation in the well conduit; said outer tubular assembly defining a seal bore in its upper portions and an annular locking recess below said seal bore; an inner tubular body assembly concentrically inserted in said outer tubular body assembly; said inner tubular body assembly having an external annular seal mounted thereon and in sealing engagement with said seal bore; and internal annular seal stack mounted in the bore of said inner tubular body assembly; a collet unit having a ring portion and a plurality of peripherally spaced locking arms; said ring portion being secured to said inner tubular body assembly and said locking arms having head portions engagable with said locking recess; a work string-carried mandrel insertable through the bore of said inner tubular body assembly; said mandrel being sealingly engaged with said internal seal stack and defining an annular space within said collet locking arms; locking block means mounted on said mandrel within said annular space and engagable with said collet locking arms to hold said locking heads in said locking recess; an external recess on said mandrel movable into alignment with said locking block means by upward movement of said mandrel to permit said locking arms to be cammed inwardly and released from said locking recess, thereby permitting removal of both said mandrel and said inner tubular body assembly from the well; and means on said mandrel defining an axially extending fluid passage having a length greater than the length of said internal seal stack; said fluid passage means being located on said mandrel to bypass fluid around said internal seal stack when said mandrel is moved upwardly after releasing said locking arm.