Patent ID: 7044241

Claim:
A method for drilling a well with a well casing as at least a portion of an elongated tubular drill string and a drilling assembly retrievable from the lower distal end of the drill string without withdrawing the well casing from a wellbore being formed by the drilling assembly, the method comprising: providing the casing as at least a portion of the drill string; providing the drill string with the drilling assembly engaged at the distal end thereof; inserting the drill string and the drilling assembly into the wellbore and driving the drilling assembly to operate at the bottom of the wellbore to extend the wellbore, the wellbore being formed having a diameter greater than the diameter of the drill string; actuating the drilling assembly to disengage from the distal end of the drill string; advancing the drill string over the drilling assembly toward total depth; removing the drilling assembly out of the wellbore through the drill string without removing the drill string from the wellbore; and leaving the casing portion of the drill string in the wellbore.