Image Number 2 for United States Patent #4887672.
An improved subsea wellhead including a wellhead housing landed at a subsea well location and having a plurality of hangers landed therein, each of the hangers having a seal assembly to define an annulus in the area between the exterior of the hanger and the interior of the wellhead housing below the seal provided by the seal assembly and a passage in said wellhead housing communicating with each of the annuli, the passages extending through the wellhead housing and communicating with the space above the upper surface of the wellhead housing, a spool connected to the upper end of the wellhead housing, inner and outer seals between the upper end of the wellhead housing and the spool to define the space into which the passages communicate, a passage extending upward through the spool to communicate the pressure changes in the space between the spool and wellhead housing to the surface, and check valves in each of the passages allowing flow upwardly therethrough and preventing flow downwardly therethrough to isolate each of the annuli from the other annuli. In a modified form individual passages with suitable sealing means are provided for each of the wellhead housing passages.
|
