Millout whipstock apparatus and method

Abstract

A millout whipstock has a cylindrical body with a stabbing nose at the bottom and a deflection shoe at the top. A drill string extending through the deflection shoe is connected to a pressure housing keyed in a torque key housing in the body. A piston, mounted in a piston housing secured in the body beneath the pressure housing, has an upper portion extending through the pressure housing and is pinned in a raised position by shear pins. A slip expander at the bottom of the piston engages slips supported adjacent openings in the side wall of the body. A fluid path extending through the drill string, pressure housing, piston housing, and piston, is closed off by a rupture disk. The body is lowered by the drill string onto a cement plug in the casing. The slips are set by applying fluid pressure in the drill string to shear the shear pins and force the piston and expander downward wedging the slips outward to grip the casing. The body is cemented in the casing by pumping cement down the drill string which bursts the rupture disk and flows to the exterior of the piston and through the bottom of the body filling the space around the stabbing nose and the interior of the body surrounding the expander assembly and lower portion of the piston. The drill string is removed and a window is cut through the side of the casing by a mill.