Abstract:Hole azimuth angle correction is very important in directional well trajectory control and target-hitting analysis. By the analysis on the relationship between geodetic coordinate and Gauss-Kruger projection coordinate; and based on the geomagnetic field spherical harmonics model, geomagnetic parameters and meridian convergence angle calculation model, the realizing way and the solving steps are put forward and corresponding calculation software are programmed. With the practical calculation and analysis, the importance of accurate calculation of geomagnetic parameters and meridian convergence angle in directional well trajectory control is shown.

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.