Milling is used to grind metal objects at the bottom of the well, trim the fish crown, and sometimes to grind shorter stuck drill collars and drill rods.
1) The role of mills
Trim and grind the top of the fish; grind stuck pipes, rods, and downhole tools. It has obvious effect on the repair andmilling of staggered fractures of casing damaged wells.
2) Classification of mills
The mills are divided into flat sole grinding shoes, concave sole grinding shoes, tapered (pear shaped) grinding shoes and guide collar eye grinding shoes.
Mill shoe is a tool for over-milling operations and milling falling objects. It is used for drilling and removing the rock, sand, cement and other deposits around the falling fish in the well during the milling operation. It can also be used to trim the top of the fish.
Mill shoes are used for annulus milling, overmilling, and flushing of stuck process pipe strings and downhole tools to remove jamming and open channels, creating necessary conditions for fishing.
Types of mill shoes are: A, B, C, D, E, F, G, H, I, J, K, L, M, N types.