Wellhead systems and methods

A well system comprising:

• a retainer ring assembly, wherein the retainer ring assembly comprises:
• a threaded retainer ring, wherein the threaded retainer ring comprises:
• internal ring threading configured to interlock with external hanger threading on a surface casing hanger to facilitate securing the retainer ring assembly to the surface casing hanger;
• and
• an external retainer groove;
• a retainer plate secured under the threaded retainer ring, wherein a lower surface of the retainer plate is contoured with radial wedges and is configured to be disposed against a hanger shoulder of the surface casing hanger;
• and
• an axial anti-rotation fastener secured downwardly through an axial fastener opening in the threaded retainer ring to abut an upper surface of the retainer plate, wherein the axial anti-rotation fastener is configured to be tightened against the retainer plate to facilitate blocking rotation between the retainer ring assembly and the surface casing hanger;
• and
• a radial retainer fastener configured to be secured through a radial fastener opening in a casing head into the external retainer groove on the retainer ring assembly to facilitate securing the casing head to the retainer ring assembly and, thus, the surface casing hanger.

A well system comprising a wellhead, wherein the wellhead comprises:

• a casing hanger configured to suspend a casing string within a wellbore, wherein the casing hanger comprises external hanger threading configured to interlock with internal tool threading in a casing running tool to facilitate manipulating the casing hanger via the casing running tool;
• a casing head;
• a retainer ring assembly, wherein the retainer ring assembly comprises:
• a threaded retainer ring that comprises:
• internal ring threading configured to interlock with the external hanger threading on the casing hanger after the casing running tool is disconnected from the casing hanger to facilitate securing the retainer ring assembly to the casing hanger;
• and
• an external retainer groove;
• and
• an axial anti-rotation fastener configured to be secured through the threaded retainer ring to facilitate blocking rotation and, thus, axial movement between the retainer ring assembly and the casing hanger;
• and
• a radial retainer fastener configured to be secured through a radial fastener opening in the casing head into the external retainer groove on the retainer ring assembly to facilitate securing the casing head to the retainer ring assembly and, thus, the casing hanger.