Apparatus and method for simultaneous drilling and casing wellbores

摘要

The present invention provides apparatus and method for drilling a wellbore wherein a pilot wellbore section is drilled with a bit which section is enlarged by a trailing underreamer to the desired size. One or more steering sections between the underreamer and the drill bit are utilized for maintaining and changing the drilling direction. Each steering section includes a plurality of independently adjustable force application devices on a non-rotating sleeve. If an expandable liner is used, then an expansion device disposed above the underreamer expands the liner during retrieval of the drilling assembly to the surface.