Naturalization of azimuth angles and coordinates in directional drilling

With the intensification of exploration and development for oil and gas,the geological environment tends to be more complex for drilling and the demand for measuring and controlling well trajectory is getting higher and higher.In order to effectively monitor and control the well trajectory,it is required to calculate the practical drilling trajectory and the designed one in the same coordinate system,in which magnetic declination and meridian convergence will be involved.This paper introduces the principle and method for determining and correcting the magnetic declination,discussing the definition and calculating method of the meridian convergence,illustrating the measuring principle of magnetic clinometers.It focuses on discussing the naturalization method of azimuth angles and coordinates.The research shows that the maximum meridian convergence is over 2°23’ in China.As of the directional well with 1000 meters of horizontal displacement,more than 41.68 meters of displacement error will be caused to the horizontal calculation of the well trajectory if the effect of the meridian convergence is not taken into account.What’s more,this paper systematically discusses some other theories and methods about the naturalization of azimuth angles and coordinates,which are of practical significance to improve the accuracy and reliability in monitoring well trajectory.