Abstract: A method for enhancing the recovery of liquid products from a wellbore having at least one laterally extending drain hole wellbore extending therefrom wherein a portion of the earth around the primary wellbore and a part of the drain hole wellbore is treated to render same essentially gas impermeable so that gas cannot prematurely cone into the primary wellbore, thereby enhancing the liquid recovery by way of the drain hole wellbore before gas reaches the drain hole wellbore.

Abstract: A method and apparatus for forming substantially horizontal drain holes into a subterranean formation from a substantially vertical cased wellbore. A casing anchor is set in the casing adjacent the formation and a whipstock is used to mill a window in the casing. A flexible drill string is then used to drill the horizontal drain hole through the window. In one modification, a deflection tool having a deflection surface which has a radius of curvature of between 11 and 28 feet is used for both the milling and drilling operations. In another modification, the milling operation is carried out with a sidetracking whipstock which is then replaced with the above-described deflection tool to carry out the drilling operation. In still another modification, a whipstock adaptor is positioned onto a sidetracking whipstock after the milling operation to convert the sidetracking whipstock into a deflecting tool having the desired radius of curvature for carrying out the drilling operation.