Abstract: A bidirectional drilling downhole steering and survey tool for detecting ferromagnetic bodies from an off vertical borehole, transmitting the signals from the downhole sensors to surface equipment while drilling, and for calculation of the range and direction to the detected ferromagnetic body for the use of the directional driller in intercepting or avoiding the ferromagnetic body. In combination with the steering and range and direction to ferromagnetic body capabilities, the downhole tool may also include sensors for detecting formation bed interface, apparatus for electric or gamma ray or radioactive logging, neutron density sensor apparatus and other formation evaluation or correlation apparatus. The downhole tools may be packaged, in either an electric line transmitted tool of MWD transmitted tool.

Abstract: A directional drilling downhole steering and survey tool for detecting ferromagnetic bodies from an off vertical borehole, transmitting the signals from the downhole sensors to surface equipment while drilling, and for calculation of the range and direction to the detected ferromagnetic body for the use of the directional driller in intercepting or avoiding the ferromagnetic body. In combination with the steering and range and direction to ferromagnetic body capabilities, the downhole tool may also include sensors for detecting formation bed interface, apparatus for electric or gamma ray or radioactive logging, neutron density sensor apparatus and other formation evaluation or correlation apparatus. The downhole tools may be packaged in either an electric line transmitted tool of MWD transmitted tool.

Abstract: A method and system for tracking a borehole by means of a probe and an externally produced magnetic field. The magnetic field is produced by a current configuration which facilitates the calculation of the magnitude and direction of the magnetic field at any point in space. In order to locate the probe, magnetometers within the probe are used to measure the magnetic field. Accelerometers within the probe allow the determination of the probe's orientation which enables the measured field vector to be compared to the calculated field vector and the probe's location thereby ascertained.

Abstract: A method of determining the orientation of a surveying instrument in a borehole from measurements of the earth's gravitational and magnetic fields wherein the azimuth angle is calculated directly without correcting an apparent azimuth. Those measurements are used to calculate the borehole axial magnetic component at each orientation of the surveying instrument in the borehole, and the borehole axial magnetic component is used, along with those measurements, to directly calculate the proper azimuth angle. In a preferred embodiment, measurements are taken at a plurality of orientations in the borehole and the borehole axial magnetic component is calculated in simultaneous equations and then compared to insure the accuracy of the azimuth computation at each orientation. The orientations are preferably non-colinear.