Application status of milling shoe of drilling-milling composite bridge plug

The selection of the milling shoe used for drilling-milling composite bridge plug is lack of basis and its design and processing are not pertinent enough. To solve these problems, literatures were investigated and field practice and experience were reviewed in this paper. Accordingly, it was put forward to adopt the plane carbide milling shoe with 5-6 blades and big end OD 95%-98% of casing ID in the drilling-milling composite bridge plug and take the combination of the carbide particles with random shapes and the molded carbide column with a particular shape as the cutting blade. Numerous practice of drilling plug indicates that all types of milling shoes commonly have the wear characteristics that the entire absence with the contact line between the bottom surface of milling shoe and the peripheral surface as the center is dominant, the wear loss of the bottom surface reduces gradually from the edge to the center and the newness of the alloy at the center of the bottom surface is the highest. The square or coning water returning channels applied abroad can retain the returning abrasive dust easily, and the water returning channel shall be more accessible. It is revealed that foreign countries are advantageous in alloy quality and welding technologies, but they are basically similar to China in structure design. It is recommended to comprehensively consider the materials to be drilled, the drilling rates, the debris sizes and the wear characteristics when the milling shoe of drilling-milling composite bridge plug is designed and processed. The research results can be used as the reference for the selection, design and processing of the milling shoe of drilling-milling composite bridge plug.