空气锤撞击应力波模拟研究

SIMULATION STUDY ON AIR HAMMER IMPACT STRESS WAVE

空气锤钻井具有转速低、钻压小、控制井斜容易、提高机械钻速、减少钻井时间和成本等优点,因而在国内外各个领域受到广泛的重视和应用。但是研制大直径、高性能空气锤仍然是目前的难题,空气锤活塞和钻头在撞击过程中产生极高应力,严重制约了空气锤尺寸的设计,导致构件寿命大大降低。根据应力波传播理论及赫兹非线性撞击理论,应用差分原理对空气锤整个撞击过程、撞击过程中活塞和钻头受力进行了模拟研究,并编制了空气锤撞击应力波的模拟程序;应用此程序就活塞中截面位置变化对其性能的影响进行了研究。通过实例分析,得出空气锤活塞中截面位置对活塞受力影响较大,对整个凿入效率影响不大的认识。

Drilling with air hammer has the advantages of low rotary rate, low WOB,being convenient to control well deviation, being able to improve ROP and reduce drilling time and drilling cost, etc. It has been extensively used in many fields all over the world. However, it is still a challenge to develop large-diameter and high-performance air hammer. The very high stress produced when the piston of the air hammer impacts on the bit has seriously restricted the design of the air hammer size, which will ultimately lead to largely-shortened working life of the hammer components. According to Stress Wave Propagation Theory and the Hertz Non-Linear Impact Theory, studies have been made using the difference principle to simulate the whole impact process of air hammer and the stress condition on piston and the bit. The corresponding simulation program for air hammer impact stress wave has been compiled. By using this program, the effects of the position of the piston's middle section on the performance of the hammer have been investigated. Finally through analysis of actual cases, it is concluded that the position of the piston's middle section greatly affects the loads/stresses exerted on the piston, but not too much influence on the final cutting efficiency.