Image Number 4 for United States Patent #7621338.
A wellhead assembly includes a tree cap having a production mandrel extending down into a production passage of a Christmas tree to form a seal. The tree has an annulus bore and an annular cavity at the upper end of the tree surrounding the upper ends of the production and annulus bore. A communication gallery leads between the annulus bore and the cavity. The tree cap also includes an annular sealing member that enters the cavity for sealing a communication gallery.