Method and apparatus for removing the inner conduit from a dual passage drill string

A removable inner conduit section adapted for use with an outer drill pipe section, said drill pipe section having a counterbored portion, comprising:

• a conduit having upper and lower ends;
• means on said conduit for engaging said drill pipe section to support the weight of said conduit within said drill pipe section, said engaging means providing an interference fit between said conduit and said counterbored portion of said drill pipe section, said engaging means being biased away from said conduit and toward said counterbored portion to permit upward movement of said conduit relative to said drill pipe section but preventing downward movment;
• and
• means on said upper and lower ends of said inner conduit for connecting said conduit to other similar conduits to form an inner conduit string, each of said similar conduits having engaging means to provide means for simultaneously removing said inner conduit string in an upward direction.

An inner conduit section used in the drilling of holes for geothermal, oil and gas wells, and the like, and adapted for attachment to a next adjacent upper conduit section and a next adjacent lower conduit section, each of said conduit sections having an upper end and lower end, said conduit sections forming an inner conduit string adapted for use with an outer drill string, comprising:

• an upper end on said conduit for connecting said inner conduit to the lower end of said next adjacent upper inner conduit;
• a lower end on said inner conduit for connecting said inner conduit to the upper end of said next adjacent lower inner conduit;
• and
• means on at least one of said ends for rotatably locking said inner conduit to said next adjacent inner conduit to provide means for removing said inner conduit string from said hole said locking means comprising a key and a keyway.

A method for removing the inner conduit from a dual conduit drill string used in drilling holes for geothermal, oil, and gas wells, and the like, to permit use of emergency or salvage procedures, comprising:

• a. providing an outer conduit section;
• b. positioning an inner conduit section within said outer conduit section by means of an interference fit;
• c. joining a plurality of outer conduit sections at joints to form an outer conduit string;
• d. joining a plurality of said inner conduit sections at lockable joints to form an inner conduit string;
• e. locking said lockable inner conduit joints;
• and
• f. exerting an upward force on said inner conduit to remove the entire inner conduit string from said outer conduit string.