U 形水平井连通过程中的相对位置不确定性分析

摘要

为了更好地使用旋转磁场测距导向系统（RM RS ）来引导两井的精确连通，进行了 U形水平井连通过程中的相对位置不确定性分析。根据RM RS在连通中的引导过程，将相对位置不确定性分为由RM RS引起的测点相对正钻井井底的位置不确定性和由测斜仪引起的连通点相对测点的位置不确定性。采用井位不确定模型，得到由RM RS和测斜仪引起的相对位置不确定性的协方差矩阵。通过坐标转换，得到同一坐标系下的总协方差矩阵，并给出由总协方差矩阵确定的误差椭球（圆）。从实例计算可以看出，连通点与正钻井井底相距101.84 m时，误差椭球的半轴长度为3.75，1.90和2.66 m ；随着钻进的进行，相距10.00 m时，误差椭球的半轴长度为0.25，0.56和0.07 m。研究结果表明，由RM RS测得的相对位置误差随钻头的钻进不再积累而是逐渐减小，同时进行相对位置不确定性分析有利于实现两井的连通，并有效地指导RM RS的使用。%To effectively use RMRS to guide the accurate intersection of two U‐shaped horizontal wells ,the relative position uncertainty in the intersecting process was analyzed .According to the guiding process of RMRS for well intersections ,the relative position uncertainty was divided into two parts :the rel‐ative position uncertainty between the bottomhole being drilled and the measure point by RMRS ,and the relative position uncertainty between the intersection point and the measure point by inclinometer .The co‐variance matrix of relative position uncertainty caused by RMRS and the inclinometer was obtained by u‐sing a borehole position uncertainty model .Through the conversion of coordinates ,the total covariance ma‐trix was obtained in the same coordinate system ,and then the error ellipsoid and error ellipse were deter‐mined on the basis of the total covariance matrix .From the example it could be determined that w hen the distance from bottom‐hole drilled to the intersection point was 101.84 m ,the lengths of semi‐axes were 3.75 ,1.90 and 2.66 m respectively .With the drilling operation ,when the distance from bottomhole to in‐tersection point was 10.00 m ,the lengths of semi‐axes were 0.25 ,0.56 and 0.07 m .The result indicated that the relative position error measured by RMRS was no longer cumulative but decreased gradually .The analysis of relative position uncertainty being made simultaneously would help the realization of the inter‐section of two wells ,and guide the use of RMRS effectively .