定向钻井过程中不同测量间距导致的轨迹误差

Different measurement spacing leading to the trajectory error during the directional drilling process

常用的测斜计算方法拟合计算出的井眼轨迹与真实井眼轨迹之间存在着误差,该误差有可能导致井眼轨迹不符合设计要求,甚至引起井眼交碰等严重事故的发生,因而认识误差产生的原因并采取措施减小误差就显得十分重要。为此分析了定向钻井过程中不同测量间距(30m、10m)计算井眼轨迹曲率拟合轨迹曲线的误差情况,以及不同测量初始井深位置(N1、N1+10m)的选择所导致的轨迹曲线的误差情况,并得出以下认识:选取适当测量间距(10m),可确保在一定长度测量间距内实现测斜计算结果与实钻轨迹的更精确吻合,从而减小测斜计算中井眼轨迹的误差。研究成果对定向井精确中靶、丛式井防碰具有一定的指导意义。

At present,the well-path calculation methods in directional drilling include the average inclination angle method,the balanced tangent method,the average angle correction method,the minimum curvature method,etc.According to their basic principle,the well trajectory is assumed as a specific curve before the fitting calculation is made through the measured data of the concrete well trajectory.However,for lack of rules to be followed in the actual drilling,there is always a certain error between the calculated and the real borehole trajectory parameters.Due to this error,the well path will become deviated away from the design requirement or even such an accident as well collision will occur.In view of this,we first analyze how such errors are caused by different measurement spacing and initial measurement positions,and then present a method of selecting the proper measurement spacing,with which the curvature of a measured curve is quite similar to that of the designed one.This method can not only minimize the error in the well-path calculation,but provide good reference for accurate target landing and well collision prevention in directional drilling.