推靠式旋转导向系统底部钻具组合动态安全评价方法

推靠式旋转导向钻进时巴掌对井壁的间歇性推靠致使钻柱处于非线性阻尼激励的复杂工作状态,剧烈的振动易引发钻柱的疲劳失效。建立考虑巴掌与井壁的接触碰撞及动态激励的底部钻具组合动应力计算模型,分析钻柱转速对钻柱动应力和钻头侧向力的影响。结果表明:钻井过程中底部钻具组合动应力和钻头侧向力处于剧烈波动状态,尤其在临界转速下运动的钻柱将产生剧烈的振动及较高水平的动应力,导致钻柱出现疲劳破坏;通过调节钻柱转速至两阶相邻转速中间值,可显著降低钻柱的振动加速度。现场试验验证了通过调节钻柱转速提高底部钻具组合动态安全的可行性,为推靠式旋转导向及同类工具安全钻进参数的优化设计提供了依据。

A dynamic evaluation method for safe operation of the bottom hole assembly with bit-push rotary steering drilling system

The intermittent push-back of the bit pads against the wellbore wall during guided drilling(or bit-push steering drilling)can make the drill-string in a state with complicated nonlinear damping excitation.The violent vibration can cause a fatigue failure of the drill-string.In this paper,a dynamic stress calculation model of the drill-string was established,considering the contact collision and dynamic excitation between bit pads and borehole wall.The calculation results show that the dynamic stress of the bottom hole assembly(BHA)and the lateral force on the drill bit during the drilling process are in a volatile state.When the drill-string is in a critical rotation speed,it will result in severe vibration and great stress that can lead to a fatigue failure of the drill-string.The vibration acceleration of the BHA can be significantly reduced by adjusting the rotation speed of the drill-string to the intermediate value of two adjacent critical rotation speeds.The field test results have verified the feasibility to improve the BHA dynamic safety by adjusting its rotation speed,which can provide a basis for the optimization design of the drilling parameters for the safe operation of the bit-push rotary steering drilling system and similar tools.