Abstract: The present invention discloses a whipstock assembly (100) for use in forming a lateral borehole from a parent wellbore. The whipstock assembly comprises a body (122) and a deflection member 120) above the body. The deflection member includes aconcave portion (111) for deflecting a milling bit during a milling operation. Disposed on a perforation plate (110) portion of the concave portion is a raised surface feature (116). The raised surface supports a milling bit above the perforation plate portion during a milling operation. This, in turn, substantially prevents frictional contact between the milling bits and the perforation plate portion during a milling operation. The present invention also provides a novel method for manufacturing a whipstock in which a cavity portion is formed behind the perforation plate by milling out the backside of the deflection member and then joining a second back cover member to the whipstock body to complete the assembly.

Abstract: A method is provided that allows the operator to re-enter a primary wellbore from a lateral wellbore after the lateral wellbore has been completed. The method generally comprises the steps of locating a cutting device such as a milling bit adjacent a tubular such as a liner within a wellbore, rotating the milling bit while maintaining an axial position of the milling bit relative to the liner to initiate an opening, and rotating and axially advancing the milling bit to complete the opening. In addition, a bottom hole assembly that facilitates re-entry into the primary wellbore from a lateral wellbore is provided. The bottom hole assembly generally includes a drill collar or other heavy pipe structure, and a mill. The mill has a body and cutting structures. The cutting structures apply lateral force against a surrounding pipe to form an initial lip through the wall of the pipe.

Abstract: Apparatus for completing a subterranean wellbore and associated methods of using provide relatively uncomplicated and convenient access to a parent wellbore lower portion from a lateral wellbore liner which extends into the parent wellbore above the lower portion. The apparatus is utilized to form an opening through a portion of the liner which overlies the parent wellbore lower portion, thereby providing access thereto. In a preferred embodiment, the apparatus includes a milling guide having an axially extending guide profile formed therein, which guide profile is capable of directing a mill toward the liner portion to form the opening. The milling guide is capable of being anchored in the liner to thereby fix its axial and rotational alignment relative to the liner portion.