Abstract
In the oil industry, directional drilling technology plays a significant role in oil-gas exploration. The key to success of directional drilling technology is locate the borehole accurately using measurement while drilling instruments. Measurement While Drilling(MWD) technology has the problems of data loss and gross error in complex down hole environment. Aiming at the problems that gross error and data missed consequences the accuracy of positioning calculation seriously, this paper presents a method of fault-tolerant integrated borehole trajectory location based on geomagnetism/IMU of MWD system. Firstly, the geomagnetic survey system is established to locate the borehole position based on tri-axis fluxgate and tri-axis accelerometer. The Inertial Measurement Unit(IMU) calculates the borehole trajectory at the same time. Then, the fault-tolerant judgment mechanism is introduced to discriminate and evaluate data loss and gross error of measurement parameters. Furthermore, Kalman Filter algorithm is implied to construct fault-tolerant integrated borehole trajectory positioning system. Finally, the simulation experiment is performed on the drilling experimental platform. The experimental result shows that the fault-tolerant integrated borehole trajectory positioning system can detect data loss and gross error effectively. In addition, the location precision of the fault-tolerant integrated positioning system can be maintained within 1 meter when the time of data missed and gross error state lasts for 6min respectively. From the simulation experiments, comparing with the position calculation of pure geomagnetism, and the method of integrated MEMS and geomagnetism, the precision of the fault-tolerant integrated location calculation is improved by 68.7% and 62.8% respectively.
Highlights
In petroleum engineering, the oil-gas drilling is entered highly challenging operating environment, such as deep wells, extent reach wells and thin reservoirs, which put forward higher requirements on oil-gas drilling technology [1], [2]
The method of combining geomagnetism with Micro-Electro-Mechanical System (MEMS) can improve the accuracy of borehole trajectory location compared with pure geomagnetic measurement
In directional drilling process, data loss caused by the limitation of the data transmission system in the condition of complex down-hole environment, and parameters gross error caused by magnetic interference
Summary
The oil-gas drilling is entered highly challenging operating environment, such as deep wells, extent reach wells and thin reservoirs, which put forward higher requirements on oil-gas drilling technology [1], [2]. Exploitation of reservoirs with smaller scale, thinner reservoirs, poorer physical properties and strong heterogeneity These technologies present higher a requirement for positioning accuracy of borehole trajectory [4]. H. Yang et al.: Fault-Tolerant Integrated Borehole Trajectory Location Method Based on Geomagnetism/IMU of MWD fluxgate [6], [7]. In the case of magnetic interference in geomagnetic measurement, effective MEMS measurements are used to correct gross error to improve positioning accuracy. The above scholars have proposed some methods to reduce magnetic interference and cumulative error. There is no effective method to solve the problem of gross errors and data loss, which result in the calculation accuracy of wellbore trajectory is not enough. Aiming at the above problems, a fault-tolerant integrated borehole trajectory location method based on the diagnostic model is proposed in this paper.
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