| 摘要 |
There are disclosed several forms of subsea wellhead equipment of the type in which casing hangers connected to the upper ends of successively smaller diameter casing strings are adapted to be lowered into and landed within the bore of a casing head, which is connected to an outermost string at the subsea level, to suspend the strings within the outermost casing of the well bore, and wherein openings in each hanger which connect the annulus between each casing string and the next outer string with the space between the hanger and the bore of the head, to permit cement returns to circulate therethrough as the string is cemented within the well bore, are adapted to be closed off, when the casing has been cemented, by means of a seal assembly lowered into and locked down within the space.
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