Method and apparatus for forming an optimized window

摘要

Methods and apparatus are described for forming a window of optimum dimensions in casing wall. A window of maximum width is cut when the center line of the mill tool is located inside of the inner diameter of the casing where a maximum amount of casing is drilled away by the mill tool. A whipstock is described which deviates the mill tool outwardly so that the center line of the mill tool is in approximately this position. The whipstock then maintains the mill tool at this approximate location until a window of desired length is cut having a substantially maximum width. The whipstock then deviates the mill tool such that the centerline is outside of the casing to drill a rathole into the formation.