油井套管对地磁场的影响实验

Experiments of the impact of casing on geomagnetic field

油井中的铁磁质套管受到地磁场磁化作用会产生磁化磁场,引起套管附近的地磁异常。通过对地磁异常的分析,可以判断邻井的方位。实验中利用套管在地磁环境中分别模拟了竖直井、斜井和水平井3种情况,研究了套管对地磁场所造成的影响,总结了套管对地磁场影响的规律。实验表明:邻井为斜井、水平井时,二者所引起的地磁场强度异常区域分布相似,且异常区域较大,所引起的磁工具面偏角异常分布也如此,在井的NW、SE方向磁场强度异常较大,在NE、SW方向磁工具面偏角异常较大;邻井为竖直井时,引起的磁场强度和磁工具面偏角异常区域较小,其分布与斜井、水平井不同,在南北方向磁场强度异常较大,在东西方向磁工具面偏角异常较大。通过磁场强度异常和磁工具面偏角异常的分布可判断邻井的方位。

Affected by magnetization of the geomagnetic field, ferromagnetic casing in oil wells can form a magnetic field that re sults in geomagnetic anomaly in the neighborhood of casing. Thus, the orientation of adjacent wells can be determined by analy zing this geomagnetic anomaly. Through simulation experiments of the abnormal geomagnetic environment caused by casing of three different well types, i.e. vertical, inclined and horizontal wells, researched the impact of casing on the geomagnetic field and summarized regulations of local geomagnetic a^omalies. Experimental results show that when adjacent wells are inclined or horizontal ones, the local geomagnetic anomaly caused by them has a similar and wider regional distribution, and anomaly of magnetic tool-face declination caused by them is distributed alike, geomagnetic field is relatively abnormal in the northwest and southeast direction of the well, while anomaly of the magnetic tool-face declination is relatively obvious in the northeast and south- west direction. When the adjacent well is a vertical one, an abnormal region of geomagnetic field and magnetic tool-face declination is relatively smaller and shows a distributional pattern different from those of inclined and horizontal wells, namely in the north south orientation geomagnetic field is relatively abnormal, while in the east-west orientation magnetic tool face declination is relatively ab normal. Thus, the location of adjacent wells can be determined jointly according to the abnormal distribution of both the local geo magnetic field intensity and the magnetic tool-face declination.