钻进深度对煤矿水平井钻柱振动特性的影响

Effects of drilling depth on the vibration characteristics of drill string in horizontal well of coal mine

煤矿水平井钻柱在钻进过程中,随着钻进深度增加,钻柱在重力作用下与井壁产生复杂的碰撞接触,由此产生的托压效应更加显著,使得钻柱动力学特性随钻进深度增加而发生明显改变,进而影响钻柱的疲劳寿命。基于岩石-钻头-钻柱-井壁耦合动力学分析模型,通过有限元动态仿真,研究了钻进至不同深度下钻柱的纵向、横向和扭转振动特性,分析了钻进过程对钻柱振动特性的影响规律。结果表明:随着钻进深度增加,钻柱纵向跳钻现象呈现“平缓—剧烈—平缓”的趋势,横向扰动呈现“小范围蠕动—大范围扰动—小范围蠕动”的特点,扭转方向剧烈涡动占比呈现先增加后减小的规律,钻柱主要动力学指标与钻进深度呈非线性关系。因此在对钻柱系统进行动态分析及优化时,不能只分析特定深度,应包含整个钻进过程。

During the drilling process in a horizontal well of a coal mine, with the increase of drilling depth, the drill string has complex collision contact with the well wall because of gravity, and the significant effect of resulting back pressure changes the dynamic characteristics of the drill string dramatically, which in turn affects the fatigue life of the drill string. In this work, based on the coupling dynamic analysis model of rock-drill bit-drill string-well wall, the longitudinal, lateral and torsional vibration characteristics of the drill string at different depths were investigated through finite element dynamic simulation, and the law of drilling process impact on the vibration characteristics of the drill string was analyzed. Our results show that as the drilling depth increased, the longitudinal bit jumping of the drill string assumed a flat, intense, and then flat again tendency, and the horizontal disturbance a small-scope creeping, large-range fluctuation, and then small-scope creeping again tendency. The proportion of violent whirling in the torsion direction increased first and then decreased. The relationship between the main dynamic indexes of drill string and drilling depth was nonlinear. Therefore, it is suggested that the dynamic analysis and optimization of the drill string system should include the entire drilling process, rather than a specific depth.