| 摘要 |
A downhole assembly and method for drilling at least on longitudinal wind ow (20) and at least on key-way (50,51) in communication with the window (20) i n a tubular wall (11) to be used in drilling multi-lateral wellbores and entry and reent ry thereafter comprising: a first millin drill bit (16) for milling at least on longitudin al window (20), at least one 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 k ey- way (50, 51) in communication with the window (20), at lest 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 orienation key-way (50,51) in communication with the longitudinally milled window.
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