International Journal of Earth Sciences and Engineering

Wu Chuan ¹, Wen Guo-Jun ², Wu Xiao-Ming ¹, Fu Xian-Cheng ², Wang Wen-Qiao ², Han Lei ², Zhang Feng ¹, Xie Hui ²

Affiliations
1 School of Engineering, China University of Geosciences, Wuhan, CN
2 School of Mechanical & Electrical Information, China University of Geosciences, Wuhan, CN

Abstract

Coal-bed methane (CBM) Wells can be divided into vertical and horizontal well. The directional well is composed of vertical section and horizontal section. In the process of vertical section drilling, the drilling tool face angle is one of the most important parameters for the correction of borehole trajectory, however, the existing calculation method for tool face angle is too complicated and it is not the best suitable method for Measurement While Drilling (MWD) system which uses the Microprogrammed Control Unit (MCU) as the core. Based on this, it is deduced from this paper that two brand-new calculating formulas for tool face angle. According to the theoretical research and experiments, a kind of optimal combined algorithm for tool face angle is achieved. This optimal algorithm is suitable for MWD system with MCU as the core and can provide more accurate and efficient data support for real-time borehole trajectory correction.

Keywords

MWD, Tool Face Angle, Taylor Expansion, Triaxial Accelerometer, Optimal Algorithm.

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Zhang Feng ¹, Wu Xiao-Ming ¹, Wu Chuan ¹

Affiliations
1 School of Engineering, China University of Geosciences (Wuhan), Wuhan-430074, CN

Abstract

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.

Keywords

Downhole, Fiber-Optic Gyroscope, North-Seeking, Borehole Trajectory, Strapdown Inertial Navigation, Coordinates.

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