A casing is provided with a sealable shifting sleeve. A whipstock isinsertable into the casing and may be supported off of the casing in apredeterminedlocation so that it is oriented toward an open window in the casing when theshifting sleeve is selectively moved upwardly. By presenting an open windowforthe whipstock oriented toward the window, a drillbit may be lowered throughthecasing to interact with the whipstock to immediately begin the drilling of thedeviated wellbore. The drillbit cuts through any cement, if present, and intotheformation. A bore is presented in the whipstock to allow production from payzones below the whipstock while it is in place. Should it become necessary,thesliding sleeve may be subsequently closed to isolate the deviated wellborewhichhas been drilled with the whipstock through the open window.
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