Abstract: A section mill is positioned below an exit guide in a drill string assembly used to mill a section of steel casing below the whipstock and which as the section mill moves down and mills along the section of casing, causes the whipstock to be lowered down adjacent the milled-out casing and allows the drill bit and drill string to be run along the surface of the exit guide and into the earth formation. Alternatively, the section mill is positioned above the exit guide in a drill string assembly after the section mill has milled out in an appropriate length of the steel casing, the tubing string pulls both the section mill and the exit guide up to a position where the exit guide is adjacent the area of formation which has been exposed by milling along the steel casing.

Abstract: A combined casing mill and whipstock or other exit guide is positioned in a drill string assembly used to mill a section of steel casing, which as the section mill mills along the section of casing, allows the exit guide to be transported adjacent the milled-out casing and allows a drill bit and drill string to be run along the surface of the exit guide and into the earth formation. In an alternative embodiment, the combination of the section mill with the exit guide is used in open hole operations having no casing.