Pump off junk mill

Abstract

A device for removing junk from a well by attaching to a tubing string a mill body with a removable milling core and lowering the assembly into a well. A movable collet and check valve are located in the milling core. The milling core can be separated from the mill body by dropping a ball bearing into the tubing and then feeding water under pressure into the tubing behind the ball bearing.

1 . A device for removing junk from a well comprising:
 a mill body coupled to a milling core;   a collet located inside the milling core; and   a check valve located in side milling core;   wherein said mill body is threaded for attachment to a tubing string for receiving water or drilling mud and being lowering into a well.   
   
   
       2 . The device of  claim 1  wherein said collet is movable. 
   
   
       3 . The device of  claim 1  wherein said milling core is located in the center of the mill body 
   
   
       4 . The device of  claim 1 , wherein the milling core is releasably connected to an end of the mill body. 
   
   
       5 . The device of  claim 1  wherein said milling core is attached to cutting blades. 
   
   
       6 . The device of  claim 5  wherein said cutting blades have an opening in the center of the blades. 
   
   
       7 . The device of  claim 4  wherein the milling core is configured to be detached from the mill body when the collet is moved. 
   
   
       8 . The device mill of  claim 7  wherein the collet is configured to be primed to be moved when a ball bearing is dropped down the tubing string attached to the top of the mill body. 
   
   
       9 . The device of  claim 8  wherein the collet is moved to disengage the milling core from the mill body when water is pumped down the tubing on top of the ball. 
   
   
       10 . The device of  claim 9  wherein the pressure of the water on the ball is between 450 psi and 550 psi. 
   
   
       11 . The device of  claim 8  wherein the pressure of water on the ball is 500 psi. 
   
   
       12 . The device of  claim 8  wherein a check valve is located between said milling core and said ball. 
   
   
       13 . The device of  claim 12  wherein the check valve in the milling core prevents fluid flow from the cutting blades to the internal cavity. 
   
   
       14 . The device of  claim 13  wherein the cutting blades are tungsten carbide. 
   
   
       15 . The device of  claim 1  wherein said mill body is releasably connected to the milling core. 
   
   
       16 . The device of  claim 15  wherein the mill body is configured to be detached from the milling core when the collet is moved. 
   
   
       17 . The device of  claim 15  wherein the collet is configured to move when a ball bearing is dropped down a tubing string attached to the end of the mill body and water under pressure is applied to the ball. 
   
   
       18 . A method of removing junk from a well comprising;
 providing a mill body;   coupling a milling core to said mill body;   locating a collet in said milling core; and   locating a check valve in said milling core;   wherein said mill body is threaded to be attached to a tubing string for receiving water or drilling mud, being lowered into a well and allowing the milling core to be controllably detached from said mill body.   
   
   
       19 . The method of  claim 18  wherein said milling core is designed to be detached from said mill body by placing a ball bearing into the tubing and feeding water under pressure into the tube. 
   
   
       20 . The method of  claim 19  wherein said water under pressure being fed to the tubing is between 450 psi and 550 psi.