Experiments of the impact of casing on geomagnetic field

Affected by magnetization of the geomagnetic field,ferromagnetic casing in oil wells can form a magnetic field that results in geomagnetic anomaly in the neighborhood of casing.Thus,the orientation of adjacent wells can be determined by analyzing 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 anomalies.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 southwest 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 abnormal.Thus,the location of adjacent wells can be determined jointly according to the abnormal distribution of both the local geomagnetic field intensity and the magnetic tool-face declination.