Subsea well casing hanger packoff system

Claim 1

An annular packoff for establishing a higher pressure metal barrier between adjacent surfaces of concentric tubular elements, said packoff comprising an assembly including: (a) a two-piece annular body having an upper component rotatably interconnected to a lower component for relative axial movement of the components in opposite directions; (b) a lock ring surrounding said upper component and expandable therefrom; (c) an annular lock ring expander mandrel surrounding said upper component above said lock ring, said mandrel having means to expand said lock ring response to an axial force exerted thereon; (d) anti-rotation means releasably secured to said lower component for preventing undesired relative rotation of said upper and lower components; (e) Annular metal seal means secured to said lower component for establishing a metal-to-metal seal between said concentric tubular elements, said seal means comprising an annular metal base having a pair of annular metal sealing lips extending upwardly therefrom; and (f) Energizer means extending from said lower component into operational position between said lips, said energizer means comprising a pair of annular legs for wedging said lips apart into pressure tight contact with said tubular element surfaces in response to an axial force exerted thereon, said legs acquiring bending energy during said wedging movement and applying said energy to said lips to maintain said pressure tight metal-to-metal contact thereof with said surfaces over extreme fluctuations in pressure to which said seal means is exposed.