子午线收敛角对定向钻进精度的影响

Effect of Meridian Convergence on Directional Drilling Accuracy

摘要:

在定向钻进井眼轨迹计算时，以前方位计算只考虑磁偏角，而没有考虑子午线收敛角对定向控制精度的影响。在井距400 m以上时，子午线收敛角最大误差可达10 m以上，说明子午线收敛角对水平定向钻进精度影响较大。文中给出了通过井口的地理坐标简便计算子午线收敛角方法，其误差在20%以内，可满足对接连通井工程需要。并通过与美国产高精度磁中靶系统RMRS在土耳其29对对接连通井工程应用进行了验证，结果中靶误差较小。说明在定向钻进井眼轨迹计算时，考虑子午线收敛角对长距离水平定向井、定向对接连通井和非开挖工程精确设计和施工具有重要指导意义。

Abstract:

In design of directional drilling trajectories, only magnetic deviations were taken into account, while effects of meridian convergences on directional drilling accuracy were not included. When the well spacing exceeds 400m, the meridian convergence will result in a maximum error of 10m, indicating a substantial impact on directional drilling accuracy. This paper presents a simplified method of meridian convergence calculation with the geographical coordinates of the well collar with an error less than 20%, which can meet the field requirements. It has been proven by use of the RMRS system that the drilling error to the target is reduced to the minimum in 29 pairs of intersected wells. It shows that consideration of meridian convergences provides important guidance to the precise design and drilling of longreach horizontal wells, intersected wells and pipeline installation wells.