Abstract: In accordance with the present invention, the polarity of the remanent magnetization of an earth formation penetrated by a bore hole is accurately determined utilizing a highly sensitive magnetometer positioned within the bore hole in a direction S within the bore hole. The magnetometer is positioned such that its response direction remains parallel to the S direction at a plurality of logging stations along the vertical extent of the bore hole. The magnetometer can be oriented at the earth's surface, or in situ, to assume a posture which will place the magnetometer in the aforementioned position at a given logging depth. The response measured is the intensity of the total contribution from the remanent and induced magnetization of the formations adjacent to the well bore.

Abstract: In accordance with the present invention, at least the polarity of the direction of the remanent magnetization of an earth formation penetrated by a bore hole is accurately measured utilizing a highly sensitive magnetometer, positioned within the bore hole so as to decrease sensitivity of the instrument to the induced magnetization of the adjacent earth formation while maintaining high resolution for detection of the natural remanent magnetization property of the formation. Preferred logging posture: the magnetometer is positioned such that its response direction is in a plane orthogonal to the earth's normal field in a given azimuthal direction.