空气锤钻具组合稳定性动力学因素分析及优化

空气锤钻井过程中由于活塞轴向冲击锤头进行破岩工作，钻柱会产生轴向振动，其中下部钻铤振动常发生以钻铤螺纹断裂为主的失效故障。文章以某井空气锤钻井钻具组合及钻井参数为例，通过有限元法，建立了空气锤钻井全井段钻柱动力学模型，从动力学出发研究下部钻具组合动力学特性，优化空气锤气体钻井钻具组合。研究结果表明：空气锤钻井主要影响下部300 m钻柱，在冲击振动弯扭共同作用下，钻铤螺纹容易产生疲劳失效，模拟结果与现场失效　情况相符。优化方案为KQC275空气锤钻井过程中上部接Ø279. 4 mm 钻铤，此时钻柱系统轴向振动最小，全井段钻柱动态钻进稳定性好，对现场空气锤钻井钻具组合方案进行了优化，预防了钻柱失效。该研究对空气锤钻井钻柱动力学行为有了明确认知以及提供了钻柱振动失效预防措施

Dynamic Factors Analysis and Optimization of Drilling Stability of Air Hammer Drill Assembly

Rock breaking is carried out by piston axial impact hammer in the process air hammer drilling, which leads to severe axial vibration of drill string, and the vibrations of lower portion of drill collar are the most complex, the most common failure was thread breakage of drill collar. In this paper, taking the BHA and the drilling parameters of air hammer drilling in a well as an example, the dynamic model of entire drill string in the hole of air hammer drilling is established through the finite element method, the BHA dynamic characteristics are studied to optimize the BHA of air hammer drilling. The research results show that length of drill string affected by vibration is approximately 300 m from bottom, the drill collar thread is prone to fatigue failure under the combined action of impact vibration, bending and torsion. The simulation results are consistent with the field failure statistics. In the process of drilling, when the top of the KQC275 air hammer is connected with a Ø279. 4 mm drill collar, the axial vibration of the drill string system is minimal, and the entire drill string in the hole shows good stability during dynamic drilling, the BHA of air hammer drilling in field is optimized to prevent the drill string failure. In this paper, the dynamic behavior of drill string in air hammer drilling has been clearly recognized and the prevention measures of drill string vibration failure have been provided.