Method of milling and drilling,and a drilling assembly

摘要

A method of milling a window through a casing in a primary well bore and drilling an enlarged sidetracked well bore comprises running into the primary well bore a drilling assembly comprising at least one cutting apparatus adapted to drill an enlarged borehole, milling a window through the casing, and drilling the enlarged sidetracked well bore, wherein the milling and drilling steps are performed in one trip into the primary well bore. A drilling assembly comprises at least one cutting apparatus operable to drill an enlarged borehole, wherein the drilling assembly is operable to mill a window through a casing in a primary well bore and drill an enlarged sidetracked well bore through the window in one trip into the primary well bore.