Underground Magnetic Navigation System

Traditional way for Coalbed methane(CBM) is surface(vertical wells) drainagebuck,but this method may cause low production of single well and the economic returnrelatively poor. In order to solve this problem, one of countermeasures to stimulateCBM production is horizontal well technology.The technology that connect the verticalwell and the horizontal well is not only the key in the CBM development,but also anbottleneck. Although there was the advanced navigation technology in other countries,because the price is expensive and blockade on techniques, precise connectiontechnology for the vertical and the horizontal well was still a big difficult problem in theCBM development.In this paper,to guide the bit drilling accurately by magnetic signalthat producted by permanent magnet arrays.And the drill collar enter the target area, toachieve the purpose that the two well intersection.This paper build modle of magnetic dipole on the basis of the the Coulomb’stheory.Starting from this modle,derived the magnetic intensity of magnetic dipole in aspatial spot x, y, z three direction.therefore obtained the magnetic intensity of thepermanent magnet arrays by futher reaserch.For the sake of filtering the geomagneticsignal and noise,design FIR digital filter based on hamming window function. Thusobtained magnetism signal which produces by the permanent magnet arrays, prepare formeasuring the angle and diatance in next step. It meet the question that the phase woulddelay when filtered the signal. Adopt the method based on waveform matching toextended data of the original signal,and then to filter the signal can effectively eliminatethe phenomenon of phase delay caused by FIR digital filter. It had compiled the FIRdigital filtering software using the VC++. The man-machine contact surface is friendlyand the function is comprehensive. Inference the Inversion Formula of the angle and thedistance with the magnetic intensity by taking the extreme value based on the magneticintensity of magnetic dipole. Extracted the undetermined coefficient between thedistance and the magnetic intensity using least-squares approximation. Usingmulti-sensor data fusion technology,fuse the data which gathered by the threemagnetism vector sensor, the measurement precision of the angle and the distancewould be enhanced futher. The field results indicated: the maximal absolute error ofdistance was0.9536m;the relative error of angle was not surpass3.4%in30m,30m to40m was not surpass4%,and the absolute error was not surpass0.4degree in50m.