Study on Downhole North-Seeking and Horizontal Hole Trajectory Measurement Technology Based on Inertial Navigation

In this paper, a system is designed to measure the angular velocity based on the triaxial fiber-optic gyroscope in order to solve the magnetic anomaly from secondary ores and metal interference in the underworking. In this system, with the magnetic factors excluded, the component of the earthly rotational angular velocity for the target point is obtained and then the corresponding north-seeking algorithm is derived. Meanwhile, with the limitations of longitude and latitude parameters removed, the geographical direction and angle to the North Pole for the target point are directly solved. In addition, the strapdown inertial navigation system consists of the triaxial fiber-optic gyroscope and accelerometer and it is used to collect the attitude data in the horizontal hole of the heading face. Then, the attitude integral calculation is deduced to solve the relative coordinates of the borehole trajectory. The data of the north-seeking system obtains the absolute spatial trend and coordinates of the downhole horizontal hole through correcting the coordinate system of the relative borehole trajectory. Moreover, this paper discusses the feasibility and limitations of the double-system integration and matching.