Abstract: A method for steering the direction of drilling for oil, gas, or other boreholes drilled in locations such that the level of magnetic interference from nearby magnetic materials or fields is so large that conventional methods using magnetic compass steering tools cannot meet required accuracies. The method is based upon using gyroscope-based survey tools having an inertial angular rate sensor with one or more axes of rate sensitivity and an inertial acceleration or tilt sensor with one or more axes of sensitivity to perform both the normal survey purpose for such tools and the steering function during drilling.The method includes the measurement of initial azimuthal direction, tilt angle, gyro tool face and high side tool face at the beginning of the borehole and the continuous measurement of one or more of these quantities as drilling progresses.

Abstract: The invention relates generally to mapping or survey apparatus and methods, and more particularly concerns efficient transmission of survey signals or data from depth level in a borehole or well to the well surface, for analysis, display or recordation; further it concerns efficient transmission of command data from a surface computer unit to the survey tool at depth level in a borehole or well for control of instrumentation operating modes, operating characteristics, or diagnostic purposes; and further it concerns supply of DC power downwardly to the instrumentation via a wireline by which such command signal and survey data or signals may be transmitted upwardly or downwardly respectively.

Abstract: The invention concerns efficient transmission of borehole survey signals or data from depth level in a borehole or well to the well surface, for analysis, display or recordation; further it concerns supply of DC power downwardly to the instrumentation via the same wireline via which such survey data or signals are transmitted upwardly.