井眼轨迹不确定性分析方法的探讨

DISCUSSION ON THE ANALYTICAL METHOD OF WELL TRACK UNCERTAINTY

文章讨论了经典的ＷｄＷ井眼测量误差分析理论的八项缺陷和不足，认为该理论不再适合于现代井眼轨迹测量误差的分析工作。根据现代井眼轨迹测量特点，从两种角度总结和概括了井眼轨迹测量误差的种类，从误差与仪器的内在关系上，可分为仪器相关误差和非相关误差；从误差本身的统计性质上，可分为系统误差、随机误差和粗差。针对目前最常用的，基于固态磁力或速率陀螺传感器的测量工具，进一步地描述了其模块意义上的七个独立误差根源，即原始传感器输出值误差、测量深度、磁偏角误差、磁干扰误差、磁化纠正误差、钻具组合下垂误差以及不同轴误差。之后文中又探讨了衡量井眼位置不确定性的重要指标—协方差矩阵的构造方法，并在此基础上介绍了如何确定井眼每一测点的误差椭球或椭圆及相应的置信水平。

In this paper,the eight drawbacks of the analytical theory for classical WdW well track measurement error are discussed and it is considered that this theory does not fit for the analytical work of presentday well track measurement error.According to the measuring characteristics of presentday well track,the error's variety in well track measurement is summarized and generalized from two points of view.It can be divided into instrumentrelated error and environmentrelated error from the inherent relation between error and instrument,and into system error,random error and gross error from the statistical nature of error itself.In the light of the most commonly used measuring tools and based on the solidstate magnetism or rate gyrosensor,the seven independent error sources have been further described,i.e.original sensor output value error,measuring depth error,magnetic declination error,magnetic interference error,magnetismcorrected error,drill string assembly droop error and uncoaxiality error.Then,the constructing method of the covariance matrixan important index for evaluating the uncertainty of wellbore's position,is discussed also.And,on the basis of that ,how to determine the error ellipsoid or ellipse as well as their corresponding believing level is introduced.Finally,the application of this method to evaluating the intersection probability of well track is introduced.