In order to study the metrical problems in gas injection wells and production wells for the vertical distance in SAGD (steam assisted gravity drainage) , the alternating magnetic field generated in the fluxgate sensor rotary magnetic beacon was applied to calculation the distance. Three axis fluxgat sensor output values were used to calculate the vertical distance between the two holes, and kept the distance between the first and second boreholes within a certain range, thus effectively made wells keep parallel. In order to compensate for the effects of perturbing magnetic fields associated with magnetized sections of the drill collar, a correction method of determining the distance which relied on the knowledge of local geomagnetic field and interference magnetic field was described in detail. The measuring experiments show that the correction method can determine an accurate vertical distance under the environment of the disturbance of magnetic material. It is simple, effective and practical, and beneficial to improving the recovery of oil resources.%针对蒸汽辅助重力泄油（SAGD）中注气井和产油井垂直距离的测距问题,提出了通过磁通门感应旋转磁信标中产生的交变磁场来进行垂直距离测距.并利用磁通门三轴感应输出值来计算2井眼之间的垂直距离,使注汽井和产油井的井眼轨迹保持在一定的范围内.由于钻具铁磁性材料会对距离测量产生误差,用当地磁场来对干扰磁场进行距离测量的校正,实验测量表明,该校正方法能在磁性材料干扰的环境下获得准确的垂直距离,具有简单、有效、实用的特征.
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