侧钻井钻柱的纵向振动与疲劳强度预测

Longitudinal Vibration and Fatigue Strength Prediction of Drill string in Side tracking Well

利用振型迭加法计算出了钻柱的纵向振动响应，使用改进的Ｒｉｔｚ向量法计算出了整体钻柱的固有频率和固有振型，考虑钻柱沿井深随机分布的接触摩擦阻力作用及泥浆的阻尼作用，提出了钻柱在非对称循环应力状态下的许用持久极限应力的计算公式，建立了钻柱疲劳强度条件，为钻柱动强度计算和安全评定提供理论依据．

The longitudinal vibration response is calculated with the model superposition method, and the natural frequency and the corresponding normal modes of the whole drillstring are calculated with improved Ritz Vector method, while considering the damping effect of mud and the contact friction resistance of drillstring which is at random along the well depth. This paper presents a formulation to calculate the permissive enduring strength limit of drillstring under nonsymmetry circling stress state,establishes the fatigue strength condition of drillstring, and provides a theoretical basis for the calculation of dynamic strength and safety evaluation of drillstring.