Patent ID: 7798251
Filing Date: 2010-09-21
Classification: E21B

Abstract:
1. In a casing-while-drilling operation wherein a casing string gripper is suspended by a top drive of a drilling rig, the casing string gripper having slips that engage the upper end of the casing string to support and rotate the casing string, a circulation system, and a bottom hole assembly releasably mounted at a lower end of the casing string for drilling a wellbore, a method of drilling and retrieving the bottom hole assembly, comprising: (a) drilling by rotating the bottom hole assembly and with the circulation system, pumping a liquid fluid through a conduit leading to a flow passage in the casing string gripper, down the casing string, out the bottom hole assembly and back up an annulus of the casing string to the circulation system; (b) retrieving the bottom hole assembly by flowing a liquid fluid downward in the annulus of the casing string and back up the casing string, causing the bottom hole assembly to move upward; and (c) while the casing string is suspended by the casing string gripper, diverting the liquid fluid flowing up the casing string to the circulation system without passing through the flow passage in the casing string gripper.