煤层气水平井磁导向钻井理论与实践

Magnetic ranging theory and practices in CBM horizontal well drilling

摘要:

基于磁导向钻井理论研究和现场实践，建立了井下钻头与靶点间的相对距离和方位定位模型，提出了距离校正方法及微弱磁信号卡尔曼定位方法，解决了煤层气水平井复杂工况环境下的远距离、高精度磁定位难题。现场试验和应用结果表明：距离校正算法能够良好地逼近无干扰下的测量值，可有效解决井下磁矩干扰带来的测量误差；单次测量值受到噪声及杂波的影响起伏波动较大，经过卡尔曼滤波后测量精度远高于单点定位算法，在距离40.06 m处可将测量误差从1.9 m降低至0.41 m；煤层气U型水平井磁导向钻井连通靶区可有效控制在排采直井?177.8 mm井筒范围内。

Abstract:

Based on the theoretical study and field practices in magnetic ranging in well drilling， a model has been constructed for determination of the relative distance and direction between the downhole drill bit and target with the distance correction method and the Kalman filtering method for weak magnetic signals proposed； thus solving the problem with long distance and high precision magnetic ranging in CBM horizontal well drilling in the complex operation environment. The field test and application results showed that the calculation method for distance correction can obtain the value well approximate to the one measured in the interference-free environment； thus eliminating effectively the measurement error caused by downhole magnetic moment. The noise and clutter had a significant influence on the value of single measurement； however， through Kalman filtering， the measurement value was more accurate than the one from single positioning calculation with the measurement error reduced from 1.9m to 0.14m at the distance of 40.06m. In magnetic ranging for the “U” type CBM horizontal well intersection， the effective target can be controlled within 177.8mm of the vertical extraction well.