煤矿井下可退式卡瓦打捞筒的研制及应用

煤矿井下卡钻、埋钻导致的孔内断钻杆事故时常发生，目前常用的公母丝锥造扣的打捞方法成功率较低，不仅耗费大量的人力物力，还会影响煤矿开采生产进度。基于此，设计了井下可退式卡瓦打捞筒，通过外筒的螺旋锥面驱动卡瓦径向卡紧断裂的钻杆，实现起拔打捞井内钻杆。卡瓦抱紧钻杆的结构设计，提高了打捞筒对断裂钻具的把持力。控制环的键槽结构设计，实现了复杂工况下可退式操作。分析了打捞作业时钻机回转扭矩产生的切应力与打捞筒强度的关系、钻机起拔力产生的正应力与打捞筒强度的关系，为打捞筒壁厚参数设计提供理论支持；分析了钻机起拔力转换为卡瓦对钻杆抱紧力的公式，验证了卡瓦打捞筒打捞孔内钻具的可行性；试制的打捞筒在山西新源煤矿井下现场进行了打捞试验，试验表明其结构设计合理，打捞性能可靠。本研究为煤矿井下处理复杂钻孔断钻事故提供新型工具，为打捞工具结构设计提供了理论依据。 

Development and application of a retractable slip overshot in underground coal mines

The stuck and buried drills in underground coal mines often lead to accidents of broken drill pipes in the holes. At present, the success rate of the commonly used fishing methods of male and female fishing tap buckle is low, which not only consumes a lot of manpower and material resources, but also affects the production progress of coal mining. Based on this, a retractable slip overshot with the structural design of the cooperation between the slips and the outer cylinder through the wedge-shaped spiral surface has been proposed, which converts the pull-out force of the drill rod into a slip overshot model that self-locks the holding force of the broken drill rod. The structural design of slips improves the overshot’s ability to hold the broken drilling tool. The keyway structure design of the control ring realizes the retractable operation under complicated working conditions. The relationship between the shear stress generated by the rotating torque of the drilling rig and the strength of the overshot, and the relationship between the normal stress generated by the pulling force of the drilling rig and the strength of the overshot are analyzed, providing theoretical support for the parameter design of the overshot wall thickness. The formula for converting the drilling rig pull-out force into the gripping force of slips on the drill pipe is analyzed to verify the feasibility of the drilling tool in the overshot hole. The trial production and field test of the overshot have been carried out in Xinyuan Coal Mine, Shanxi Province. The successful application of the slip overshot in coal mines shows that its structure design is reasonable and its salvage performance is reliable. This study provides new technical equipment for dealing with complex drilling accidents in underground coal mine and theoretical basis for structural design of fishing tools.