近钻头扭转冲击器破岩机理及应用

Rock fragmentation mechanism and application of near-bit torsion impacter

PDC钻头是超深井硬地层主要的破岩工具。由于黏滑振动引发的PDC钻头过早失效是造成超深井钻井成本增加的一个重要因素。本文针对PDC钻头的黏滑振动效应,理论分析了黏滑振动机理,建立了PDC钻头黏滑振动系统的力学模型,并用高频低幅扭转冲击器及优化钻头结构的方式来消除钻头的黏滑振动。研究结果表明:PDC钻头长度越长,能量衰减越快,扭转冲击能量传递效率越低;PDC钻头截面积越大,长度越小,高频扭转冲击器冲击系统能量传递效率越高。新疆塔里木盆地XK3井试验表明,扭转冲击工具与常规钻具相比机械钻速提高1倍以上,能够有效消除PDC钻头的黏滑振动效应,减轻钻柱扭转振荡,降低钻井成本。

PDC bit is the main rock-breaking tool in hard formation of ultra-deep wells. Its premature failure due to the stick-slip vibration is an important factor that results in increasing the drilling cost in ultra-deep wells. According to its stick-slip vibration effects, this paper analyzed stick-slip vibration mechanism theoretically, established the mechanical model of PDC bit stick-slip vibration sys-tem, and used high frequency-low amplitude torsion impact generator and bit structure optimization, for eliminating the drill stick-slip vibration. The results show that：length of PDC bit is longer, as a result, energy decays faster and energy transfer efifciency of torsion impacter is lower;section area is larger, as a result, length is smaller and energy transfer efifciency of high-frequency torsion impacter system is higher; Xinjiang Tarim Basin XK3 Well tests show that torsional impact tools could improve penetration rate more than doubled compared with the conventional drilling, could eliminate the stick-slip vibration effects of PDC bit, and could reduce the drilling string torsion oscillations and the drilling cost.