Patent ID: 7287603

Claim:
A drilling assembly comprising: an upper drill string and a lower drill string; a fluid passage extending through the upper drill string and the lower drill string for distributing fluid to a bottom hole assembly at the lower end of the lower drill string; the upper drill string having an upper end connectable to a drilling apparatus and fluid source and having a lower end with an attached casing expander unit that communicates the fluid passage of the upper drill string with the lower drill string; the lower drill string having an upper end formed from a casing string telescoped over the casing expander unit; a constriction connecting the casing string with the rest of the lower drill string; and a flow restriction device in the lower drill string to control flow of fluid through the fluid passage; wherein the flow restriction device is operable to create a pressure in the fluid passage that acts at the constriction to advance the lower drill string past the upper drill string while simultaneously expanding the portion of the casing string moving past the expander unit.