FORCE ANALYSIS AND IMPROVEMENT DESIGN OF DOWNHOLE MILLING PIPE STRING OF SCREW DRILL TOOL

The downhole milling pipe string of screw drill tool will produce great reverse torque while milling and grinding the bridge plug, cement plug and so on, and which is extremely harmful to the screw drill tool. Based on the analysis to the forces exerted on the milling pipe string, the paper presents the improvement design, that is, the downhole antitorsion device is collocated with the downhole milling pipe string. This has effectively reduced the harm resulted from the reverse torque, and improved the force condition of the downhole milling pipe string.