| 摘要 |
A joint of tubular casing with a pre-formed window in its sidewall has a tubular sleeve fixedly attached to the interior of the tubular casing by a plurality of shearable set screws. The exterior surface of the sleeve is sealed to the interior surface of the tubular casing on opposing sides of the window. The window is filled with a fluid, and then the window is covered with one or more layers of a composite material such as fiberglass. In use, the joint of tubular casing is run down to the depth of interest in an earth borehole, and then the window is oriented with respect to the formation of interest at the depth. The joint of tubular casing is then cemented in place, after which the tubular sleeve is retrieved by the use of a fishing tool, causing the set screws to shear upon the upward movement of the fishing tool. After the interior sleeve is retrieved, a whipstock is lowered into the cased borehole, until it is oriented and anchored therein. The assembly automatically fixes the axial and circumferential orientation of the whipstock within a surrounding casing joint and holds the assembly in place. Alignment and fixing of the whipstock ensures proper engagement and orientation of a drill bit with an access window formed in the casing wall. A drilling assembly is lowered into the casing and a lateral bore is drilled off the whipstock through the composite material and into the surrounding formation.
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