SUBSEA WELLHEAD PROVIDING CONTROLLED ACCESS TO A CASING ANNULUS

摘要

A subsea wellhead assembly includes a wellhead body (1) which disposed to support an isolation sleeve (39) for a production tree and to support below the isolation sleeve a production casing hanger (21) for a production casing string. The body also supports a second casing string outside the production casing string whereby to form an annulus (22) between the casing strings. The body includes a passageway (25) which is in communication with the annulus near a lower end of the body and extends upwardly within the wall of the body towards the upper end of the body. A valve (27) is accommodated in the upper part of the body and provides controlled communication between the passageway (25) and a port (43) which can be coupled to the isolation sleeve. The valve is controllable from a production tree and in particular is moveable between an open position and a closed position in response to fluid pressure applied to the valve from a production tree by way of the isolation sleeve.