The present invention relates to an improved subsea wellhead hanger and seal. Prior to the present invention subsea wellhead hangers have included a shoulder which lands on the housing seat with a shoulder facing upwardly and forming the lower end of an annulus in which the hanger seal is positioned. This prior structure allows the circulation of fluids upwardly through the annular space between the hanger and the housing and through mud slots which extend through the hanger body from a position below the landing shoulder to the annulus above the shoulder. An example of this type of structure is disclosed in U.S. Pat. No. 4,550,782.
Seal structures have varied widely and include resilient annular seal which is compressed axially to expand it into sealing relation with the interior and exterior walls of the annulus. U.S. Pat. No. 3,664,689 illustrates this structure. Another form of seal includes legs which are wedged outward into sealing engagement with the walls as shown in U.S. Pat. Nos. 4,595,053 and 4,131,287. These seals provide a metal-to-metal seal.