Wellhead system

A wellhead system for supporting a plurality of casings in an oil or gas well, comprising:

• a wellhead housing having an outer casing string secured thereto,
• a casing hanger having an inner casing string secured thereto,
• a shoulder within said wellhead housing having a plurality of circumferentially spaced support shoulder arcs,
• a shoulder on said casing hanger having a plurality of circumferentially spaced support shoulder arcs,
• whereby said support shoulder arcs within said wellhead housing and said support shoulder arcs on said casing hanger cooperate to allow said casing hanger support shoulder arcs to be positioned below the wellhead housing support shoulder arcs in a first orientation.

A wellhead system for supporting a plurality of casings in an oil or gas well, comprising:

• a wellhead housing having an outer casing string secured thereto,
• a casing hanger having an inner casing string secured thereto,
• a support groove within said wellhead housing,
• a contractible split ring on said casing hanger,
• said support groove within said wellhead housing and said contractible split ring on said casing hanger cooperating to allow said casing hanger split ring to be supported on said wellhead housing support groove after said inner casing string is tensioned.

A wellhead system for supporting a plurality of casings in an oil or gas well allowing installation of a wellhead housing over a previously installed casing hanger and connection to an outer casing string, comprising:

• a casing hanger having an inner casing string secured thereto,
• a wellhead housing sized to fit said outer casing string,
• a shoulder within said wellhead housing having a plurality of circumferentially spaced support shoulder arcs,
• a shoulder on said casing hanger having a plurality of circumferentially spaced support shoulder arcs, and
• whereby said support shoulder arcs within said wellhead housing and said support shoulder arcs on said casing hanger cooperate to allow said casing hanger support shoulder arcs to be positioned below the wellhead housing support shoulder arcs when said wellhead housing is installed on said outer casing string.

A wellhead system for supporting a plurality of casings in a oil or gas well allowing installation of a wellhead housing over a previously installed casing hanger and connection to an outer casing string, comprising:

• a casing hanger having an inner casing string secured thereto,
• a wellhead housing sized to fit said outer casing string and positioned around an outer circumference of said casing hanger,
• a support groove formed on an inner circumference of said wellhead housing,
• a contractible split ring mounted on said outer circumference of said casing hanger, and
• said support groove within said wellhead housing and said contractible split ring on said casing hanger cooperating to allow said casing hanger split ring to be supported on said wellhead housing support groove after said inner casing string is tensioned.