轴向拉力作用下复合钻柱允许扭转圈数的计算方法

深井、超深井钻井中经常使用复合钻柱,如出现卡钻等井下故障,处理时需要计算复合钻柱允许扭转圈数,但目前尚没有关于复合钻柱允许扭转圈数的计算方法。为此,从材料力学基础理论入手,建立了复合钻柱各分段最大剪切应力与几何尺寸之间的数学关系式和各分段谁先达到许用值的判定式,并推导出了在轴向拉力作用下的复合钻柱允许扭转圈数计算式。实例验算表明,推导出的轴向拉力作用下的复合钻柱允许扭转圈数计算式具有科学性和合理性,对处理深井、超深井复合钻柱卡钻等井下故障具有指导作用。 

Calculation Method of Allowable Torsional Rotating Number of Compound Drill String under Axial Tension

Compound drill string is often used in deep and ultra-deep well drilling.If downhole complicate conditions as drill string sticking occurs,allowable torsional rotating number needs to be calculated when dealing with these conditions,but so far there is not a calculation method for it.Therefore,proceeding from the material mechanics theory,this paper established mathematic relationship between maximum shear stress and geometrical dimension of the combination string,and evaluted which section reaches allowable value first,then the formula to calculate allowable torsional rotating number was derived.Examples of checking calculation showed that the formula was scientific and reasonable,could provide guidance when dealing with drill string sticking in deep and ultra-deep wells.