Coupling assembly for submarine casing sections

摘要

This invention relates to a coupling assembly by which sections of well casing disposed beneath the floor of the sea or ocean can be detached from each other at a time when a well is to be cemented in, and it is desired to remove the wellhead structure and the sections of casing extending thereabove to a drilling platform. The coupling assembly comprises an upper casing section, a lower casing section, and an external coupling sleeve slidably telescoped over the lower end of the upper casing section and the upper end of the lower casing section. An internal collar is slidably positioned within the external sleeve at a location between the casing sections, and includes an annular ring projecting over and around an end portion of the lower casing section within the external coupling sleeve. An expandable locking element is positioned between said annular ring and the upper end portion of the lower casing section. The annular ring and the expandable locking element bear against an internal shoulder formed in the external coupling sleeve, and function to interlock the external coupling sleeve to the lower casing section. A frangible retaining element extends between and interengages the internal collar to the external coupling sleeve when the annular ring and expandable locking element are in their interlocking status, and is severable to permit the internal collar to be moved axially within the external coupling sleeve to facilitate disengagement of the coupling sleeve from the lower casing section.