| 摘要 |
A wellbore sidetracking method has been invented which includes, in certain embodiments, milling out a casing section from a cased, cemented wellbore; placing a deflection device, e.g. a whipstock, so that, upon pivoting of the upper concave portion of the whipstock at least a top portion thereof extends up into and abuts casing above the milled out section and, in certain aspects, a portion of the whipstock also extends down into and abuts casing below the milled out section; introducing a mill into the wellbore to mill out a part of the casing above the milled out section which would interfere with the introduction of a drill bit; removing the mill; introducing a drilling system into the wellbore to be deflected into the milled out area; and drilling a new sidetracked bore with the drilling system from the milled out area. In one aspect a mill is provided which mills out the part of the casing above the milled out area without contacting the formation or with only minimal contact thereof.
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