Risk analysis and measurements optimization for two casing milling modes of permanent packer in deep deviated well

Pemanent packer for underground treatment is needed or capability demand of marine workover rigs in overhaul operation of deep deviated well. Adopting grinding and milling mode has some disadvantages such as difficult treatment,long period and high cost. Therefore casing milling mode,which mills slips and seal sleeves of drillble permanent packer then has salvage and recovery or pushes down to artificial bottom hole untilnot influencing next oper-ation, is usually adored Target against permanent packer of deep deviated well, two different dynamic driving modes are adopted to have milling treatment from actual situation of operation well. One is ground ground rotary table drive,which may put big bit pressure because all drilling tools are in rotating state with whole friction and big torsion distance, the other is under:ground motor drive, that is, drilling tools rotates below motor but above motor to reduce friction However, bit pressure imposed is small or motor stall is easily a roused. Therefore the motor stall is easily aroused.Therefore, the motor performance requirement is higher.Criterion recognition if casing milling succeeds is put forward by risk comparative analysis on casing milling and optimization of two casing milling bit tools and parameters, which offers reference or field application.