Patent ID: 7306056

Claim:
A method of forming a branch wellbore from a main wellbore having a casing in at least a section of the well, comprising: (a) providing a bottomhole assembly (BHA) including a drill bit, a force application member, and a mill separate from the drill bit, the mill having at least one expandable cutting element; (b) conveying the BHA into the wellbore with a drill string; (c) positioning the mill adjacent the cased section of the main wellbore; (d) cutting a portion of the casing with the mill by expanding the at least one cutting element, a substantially open hole portion being formed thereby; (e) manipulating the drill string to position the drill bit adjacent the open hole portion; (f) operating the force application member to guide the drill bit into the open hole portion; and (g) drilling the branch wellbore with the drill bit.