Milling apparatus and method for well casing

A method of operating a well penetrator for drilling a hole through a well casing wherein said well penetrator includes a sequence valve having a plurality of operating positions, a two position extend valve, an oil damper assembly, a large carriage index up hydraulic cylinder, small carriage index down hydraulic cylinder means, a carriage assembly connected to said hydraulic cylinders, a lance guide supported at one end on said carriage assembly, a high pressure lance slidably mounted within said lance guide, a hydraulic motor supported on said carriage assembly, a mill bit rotatably driven by said hydraulic motor and being axially movable by a piston having an extend chamber on one side of said piston and a retract chamber on a side of said piston opposite from said one side, and a kickover assembly having means for moving said mill bit into proximity with said well casing;

• the method including the steps of:
• 1) pumping pressurized hydraulic working fluid to said retract chamber and to said small carriage index down hydraulic cylinder means;
• 2) increasing the pressure of the working fluid to a first predetermined pressure to actuate said sequence valve to an operating position wherein pressurized hydraulic working fluid passes through said sequence valve to said hydraulic motor, said large carriage index up hydraulic cylinder and said kickover assembly;
• 3) further increasing the pressure of the working fluid passing through the sequence valve to a second predetermined pressure higher than the first predetermined pressure to actuate said extend valve to an open position wherein pressurized hydraulic working fluid passes through said extend valve to said oil damper assembly causing a controlled increase in pressure supplied to said extend chamber;
• 4) reducing the pressure of the working fluid passing through the sequence valve to the first predetermined pressure to allow the extend valve to return to its closed position wherein pressure is exhausted from said oil damper and said extend chamber;
• 5) further reducing the pressure of the working fluid passing through the sequence valve until the sequence valve is actuated to an operating position wherein pressurized working fluid is no longer provided to said hydraulic motor, said large carriage index up hydraulic cylinder or said kickover assembly.

A well penetrator tool comprising:

• 1) an elongated support means positionable in a well casing having an axis and a casing inner surface for lowering down the casing to a desired depth;
• 2) carriage means mounted on said elongated support means for selective movement between an upper position and a lower position relative to said casing;
• 3) a driven rotary milling cutter mounted on said carriage for rotation about a cutter axis having a substantial component perpendicular to the axis of the casing and for inward and outward movement along said cutter axis so that outward movement results in the cutting of a casing opening in said casing by said milling cutter when said carriage is in its upper position;
• and
• 4) hose guide means on said carriage supporting the outer end of a movable hose having a nozzle on its outer end in alignment with said casing opening in response to said carriage being in its lower position whereby the hose can be extended outwardly through said casing opening while ejecting high pressure fluid from its nozzle end to cut a passageway into the surrounding formation.