Patent ID: 7845417
Filing Date: 2010-12-07
Classification: E21B

Abstract:
1. A method of retrieving a downhole tool releasably connected to a lower end of a string of casing during a casing-while-drilling operation, comprising: (a) suspending the casing in the well from a drilling rig floor opening; (b) running a string of conduit into the casing while it is suspended and engaging and retrieving the downhole tool; (c) when circulation is desired while the conduit is located within the casing, securing a circulation tool to an upper end of the conduit, lowering the conduit and the circulation tool, and with the circulation tool, closing off an upper end of an inner annulus between the conduit and the casing; and (d) circulating fluid down through the circulation tool and the conduit and back up an outer annulus surrounding the casing.