摘要 |
A downhole assembly and method for drilling at least one longitudinal window (20) and at least one key-way (50, 51) in communication with the window (20) in a tubular wall (11) to be used in drilling multi-lateral wellbores and entry and reentry thereafter comprising: a first milling drill bit (16) for milling at least one longitudinal window (20), at least a first whipstock (10) having at least one guide surface (18), orientation and positioning members (14, 19, 33) located on the first whipstock (10) for orientating and positioning tools (22, 35) to be used in drilling and milling at least one key-way (50, 51) in communication with the window (20), at least one guide surface member (18) on the first whipstock member (10) for guiding the first milling drill bit (16) for milling the window (20), second drill bit mounted either in a second whipstock or a milling drill bit housing member (34) for drilling a downhole orientation key-way (50, 51) in communication with the longitudinally milled window.
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