A bi-centre bit for drilling out through a casing shoe

摘要

The present invention is a bi-center drill bit designed to drill out the cement and other material in the casing and then proceed to drill out the full gauge drilling diameter borehole with a diameter greater than the inside of the casing. The bi-center drill bit is configured with non-drilling bearing elements (68,168) that contact with the casing when the bit is drilling the cement without allowing the gauge cutting elements (24,124) of the bi-center drill bit to contact the casing. The bi-center drill bit also has a cutting element configuration which prevents reverse scraping of the cutting elements when drilling both the cement and the formation. <IMAGE>