CIRCULATION SYSTEM FOR RETRIEVAL OF BOTTOM HOLE ASSEMBLY DURING CASING WHILE DRILLING OPERATIONS

摘要

During casing-while-drilling, drilling fluid is pumped through a conduit leading to a flow passage a casing string gripper and down the casing string. A bottom hole assembly is mounted at a lower end of the casing string for drilling a wellbore. The bottom hole assembly is retrieved by mounting a circulation sub to the casing string below the casing string gripper, the circulation sub having a lateral outlet. A return flow line is connected from the outlet to the circulation system. The operator flows fluid downward in an annulus of the casing string and back up the casing string, causing the bottom hole assembly to move upward. The fluid flowing back up the casing string is diverted through the outlet in the circulation sub to the circulation system without passing through the flow passage in the casing string gripper.