Jars is widely used to solve the sticking incident in the drilling process.Accurate shock load calculation can guide the selection of the construction parameters of the operation,the placement of the jars and BHA design,to achieve the best shock effect.Conventional hydraulic dynamic load calculation method is not considering the impact of friction on stress wave spreading in the drillstring.In actual operating process,friction resistance caused by the irregularity of the wellbore and eccentricity of drillstring in the wellbore,viscous resistance caused by the movement of the drillstring in drilling fluid,makes the drillstring acceleration process exhibiting damped vibration characteristics.To solve this problem,drillstring damping vibration model is established,analysis of dynamics of acceleration process of jarring is made,displacement and velocity equation is deduced longitudinal acceleration process,and maximum velocity of drillstring before the collision is being calculated.According to the law of conservation of energy and momentum conservation,shock acting on the stuck point shock force is deduced.This calculation model is satisfied with the actual force of the drillstring in the wellbore environment during jarring operation.%震击器被广泛用于解决钻井过程中的卡钻事故.准确计算震击器的震击载荷对作业中施工参数的选取、震击器安放位置及钻具组合设计具有重要的意义.传统液压震击器动载荷计算方法中,未考虑阻尼力对震击过程的影响.实际震击作业过程中,由于井筒不规则性及钻柱在井筒中偏心对钻柱造成的摩擦阻力、钻井液对钻柱运动产生的黏滞阻力,使钻柱上提加速过程呈有阻尼振动特性.针对这一问题,建立了钻柱阻尼振动力学模型,进行震击加速过程的整体动力学分析,推导出纵向加速过程的位移及速度方程,计算出震击碰撞前钻柱上行最大速度.采用能量守恒定理及动量守恒定理,推导出作用于钻柱卡点处的震击力计算方法,计算模型更接近震击作业中钻柱的实际受力情况.
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