Downhole milling machine and method of use

The method for forming an opening in the housing of a tubing-retrievable subsurface safety valve of claim 17, wherein the housing system comprises a plurality of sub-housings.

The method for forming an opening in the housing of a tubing-retrievable subsurface safety valve of claim 18, wherein the drive system comprises:

• a rotary motor;
• and a drive shaft system having a first end and a second end, the first end being mechanically coupled to the rotary motor, and the second end being connected to the cutting system.

The method for forming an opening in the housing of a tubing-retrievable subsurface safety valve of claim 19, wherein the cutting system comprises at least one blade for shaving the inner surface of the pressure containing body of the tubing-retrievable subsurface safety valve until an opening has been formed in the pressure containing body.

The method for forming an opening in the housing of a tubing-retrievable subsurface safety valve of claim 20, wherein the blade is rotated by the drive shaft system.

The method for forming an opening in the housing of a tubing-retrievable subsurface safety valve of claim 21, wherein the at least one blade is configured to form an eccentric opening within the pressure containing body of the tubing-retrievable subsurface safety valve.

The method for forming an opening in the housing of a tubing-retrievable subsurface safety valve of claim 22, wherein each of the plurality of blades is disposed on a cutter member having a cam lobe at an upper end.

The method for forming an opening in the housing of a tubing-retrievable subsurface safety valve of claim 21, wherein:

• the actuating system comprises a magnet, and a switch sensitive to the magnet;
• and the housing system is configured such that the magnet and the switch are moved into proximity with one another after the housing system is landed into the bore of the pressure containing body of the tubing-retrievable subsurface safety valve.

The method for forming an opening in the housing of a tubing-retrievable subsurface safety valve of claim 25, wherein:

• the rotary motor is a DC motor;
• the drive system further comprises one or more batteries for powering the motor;
• and the drive system also further comprises a controller for controlling the motor.

The method for forming an opening in the housing of a tubing-retrievable subsurface safety valve of claim 26, wherein:

• the switch is a reed switch responsive to a magnetic force;
• and the reed switch provides electrical communication between the batteries, the controller and the motor in response to the magnetic force provided by the magnet when the magnet and the reed switch are brought into sufficient proximity with one another.

The method for forming an opening in the housing of a tubing-retrievable subsurface safety valve of claim 27, wherein the step of initiating the actuating system is performed by applying downward pressure to the milling tool in order bring the switch and the reed magnet into sufficient proximity with one another.

The method for forming an opening in the housing of a tubing-retrievable subsurface safety valve of claim 21, wherein the plurality of subhousings of the housing system comprises:

• a motor housing for housing the motor;
• a switch housing having a central bore for receiving a portion of the drive shaft system, and a second cavity for housing the reed switch;
• and a cutter head housing for housing the cutting system.

The method for forming an opening in the housing of a tubing-retrievable subsurface safety valve of claim 29, wherein the switch housing further comprises a first cavity for housing a pressure balancing piston, the first cavity having a dielectric fluid above the piston, and being exposed to wellbore pressure below the piston.

The method for forming an opening in the housing of a tubing-retrievable subsurface safety valve of claim 30, wherein the plurality of subhousings of the housing system further comprises a sliding sleeve, the sliding sleeve receiving a portion of the switch housing as the milling tool is landed into the bore of the pressure containing body of the tubing-retrievable subsurface safety valve, in order to telescopically reduce the length of the housing system.

The method for forming an opening in the housing of a tubing-retrievable subsurface safety valve of claim 31, wherein the plurality of subhousings of the housing system further comprises:

• a thermal housing for housing the one or more batteries and the controller;
• and a flask connector for connecting the thermal housing and the motor housing.

The method for forming an opening in the housing of a tubing-retrievable subsurface safety valve of claim 32, wherein the actuating system further comprises an electrical connector for placing the motor and the batteries in electrical communication, the electrical connector being housed in the flask connector.