No abstract

To obtain the real-time drilling trajectory of radial horizontal jet drilling (RHJD), a magnetized nozzle localization method based on magnetic gradient tensor (MGT) is proposed. The MGT system consisting of five tri-axial magnetometers, a tri-axial accelerometer, and a tri-axial gyroscope are installed in the casing. The magnetized nozzle is made of a strong magnetic permanent magnet whose position can be obtained by measuring the MGT generated by itself at the measurement point. The simulation and experiment of the localization method are carried out, which show that the method has high accuracy. When the detection distance is 40 m, the error is only 0.07 m, which meets the requirements of engineering practice. The accuracy of the magnetometer, the baseline distance and the magnetization strength of the nozzle are the main factors affecting the localization error. This localization method can meet the requirements of positioning accuracy in practical engineering, which greatly avoids the drilling failure of RHJD and has a wide application prospect.

Uniaxial magnetoresistive sensors based on the HMC1001 can realize acquisition, processing, and display of magnetic signals, with measurement error controlled to within 1 %, basically satisfying application requirements for positioning of the pig labeled with magnets. Given that the HMC1001 sensor has only one sensitive axis, to ensure real-time detection of the maximum magnetic fluctuation when the pig passes, according to the one-dimensional coordinate classical positioning method for uniaxial magnetic sensors, the horizontal east–west direction pipeline is first modeled, and the magnetic fluctuations in the horizontal and vertical directions are calculated. The results show that fluctuations in the vertical direction were slightly larger than those in the horizontal. For other angles between horizontal and vertical, the angle variable is introduced, and the comparison reveals that the magnetic fluctuation curve smoothly transitions from horizontal to vertical. The optimal detection attitude of the pipeline in any direction is then simulated by using the same method, revealing that the vertical magnetic value is the largest. Finally, related equivalent experiments are conducted, and the experimental curves are basically consistent with the simulations. Therefore, it can be concluded that the HMC1001 sensor should be installed perpendicular to the pipeline for optimal detection when positioning the pig.