Patent ID: 8430187
Filing Date: 2013-04-30
Classification: E21B

Abstract:
1. A process for drilling a sidetrack wellbore out of the side of an existing wellbore above the bottom of the existing wellbore where the process comprises: a) installing a drillable billet into an existing wellbore at a desired location for stepping out of the existing wellbore and beginning the sidetrack wellbore, where the billet is made of a drillable material, where the billet has a long, generally cylindrical body that is suited and sized for insertion into the existing wellbore, where the billet blocks the wellbore below the location of the billet, where a path is formed in the billet, where the path is shaped as an angled trough that is arranged to direct anything descending down the wellbore to a preferred side of the wellbore; b) lowering a drillstring with a bi-centered drill bit into the existing wellbore down to the location of the billet where the bi-centered drill bit includes a pilot drill portion suited for drilling into the earth and for following the path in the billet and at least one wing portion extending radially outwardly from the pilot drill portion suited for reaming out a hole larger than the pilot drill portion, where the diameter of the path is similar to the diameter of the pilot drill portion in order to provide stability to the drillstring as the drill bit rotates with the pilot drill portion in the path; and c) rotating the bi-centered drill bit and lowering the drillstring so as to direct the drill bit so that the pilot drill portion follows the path and the wing portion reams out at least part of the billet and also into the earth to form the sidetrack wellbore through the side wall of the existing wellbore into the earth.