Importance

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Abstract

A pack-off assembly (P) for a wellhead system (W) comprising of a pack-off nut (36) with a tapered pack-off (40). The pack-off nut (36), in one embodiment, contains an internally tapered split ring (44) having multi-start threads (46) for engaging similar mating multi-start threads (32) on the casing hanger (C). The casing hanger (C) external surface (20) is provided with a taper which faces the surrounding internal cylindrical wall (16) of the wellhead (W) thus providing a tapered annulus (14). The pack-off assembly (P) is lowered to the wellhead (W) in a running tool (T) where the pack-off (40) is moved into the tapered annulus (14) without rotation of the pack-off nut (36) and the pack-off nut (36) is stabbed over (the mating threads (32, 46) ratchet) by the weight of the tubing string. Thereafter, system fluid pressure moves the pack-off assembly (P) further into the annulus (14) where the pack-off (40) engages an abutment and is compressed and expanded into sealing relationship with the internal and external surfaces of the annulus (14), respectively providing both a metal-to-metal seal and an elastomeric seal. In another embodiment, the ring is a serpentine ring (44a) with multi-start threads (46a). In still another embodiment, the split ring (46b) with the multi-start threads (46b) is provided with ramp-type thread locking means (92, 94).

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First Claim