Abstract: Techniques for mitigating magnetic sensor errors are contemplated. In some aspects, the disclosed technology provides a method for reducing measurement errors in a directional module of a drilling system that includes steps for: receiving a current measurement from a current sensor, wherein the current measurement is associated with electrical current received at the current sensor via a first conductive branch and a second conductive branch, receiving a field measurement from a magnetic sensor, and associating the current measurement from the current sensor with the field measurement from the magnetic sensor. Systems and machine-readable media are also provided.

Abstract: An apparatus for generating electricity includes a flexural member configured to flex upon being subject to a vibration. A plurality of weight displacement systems is disposed at the flexural member, each weight displacement system in the plurality being configured to displace a moveable weight upon receipt of a signal. A processor is configured to provide a signal to each weight displacement system in order to achieve a desired resonant frequency of the flexural member. And, an electricity generating device is coupled to the flexural member and configured to generate the electricity upon flexing of the flexural member.

Abstract: An apparatus for generating electricity includes a flexural member configured to flex upon being subject to a vibration. A plurality of weight displacement systems is disposed at the flexural member, each weight displacement system in the plurality being configured to displace a moveable weight upon receipt of a signal. A processor is configured to provide a signal to each weight displacement system in order to achieve a desired resonant frequency of the flexural member. And, an electricity generating device is coupled to the flexural member and configured to generate the electricity upon flexing of the flexural member.

Abstract: The present invention provides a method for determining magnetometer errors during wellbore survey operations. It is capable of determining errors on up to three axes, with or without the use of an external reference measurement of the local magnetic field, and is capable of providing an accurate result using data from a minimum number of surveys. A model is used to correct the observed data and the corrected data are transformed from the tool coordinate system to a different coordinate system referenced to the earth. The difference between the corrected transformed data and reference data in the earth coordinate system is minimized to determine the model parameters. The present invention also provides a method for determining residual uncertainty in the measurements and for quality control of the measurements.

Abstract: The present invention provides a method for determining magnetometer errors during wellbore survey operations. It is capable of determining errors on up to three axes, with or without the use of an external reference measurement of the local magnetic field, and is capable of providing an accurate result using data from a minimum number of surveys. A model is used to correct the observed data and the corrected data are transformed from the tool coordinate system to a different coordinate system referenced to the earth. The difference between the corrected transformed data and reference data in the earth coordinate system is minimized to determine the model parameters. The present invention also provides a method for determining residual uncertainty in the measurements and for quality control of the measurements.

Abstract: This invention provides a measurement-while-drilling (MWD) downhole assembly for use in drilling boreholes which utilizes gyroscopes, magnetometers and accelerometers for determining the borehole inclination and azimuth during the drilling of the borehole. The downhole assembly includes at least one gyroscope that is rotatably mounted in a tool housing to provide signals relating to the earth's rotation. A device in the tool can rotate the gyroscope and other sensors on the tool at any desired degree. A processor in the tool combines measurements from the sensors taken at a plurality of positions at the same depth to determine the systematic bias in the sensors before further processing. Accelerometers in the MWD tool provide gravity measurements from which the toolface and inclination are determined. The unbiased gyroscopic measurements are used in conjunction with the tool face and inclination measurements to determine the azimuth and tool face with respect to true north.

Abstract: A processor uses signals from at least two GPS receivers and a 3-component accelerometer located on a stable non-magnetic platform to determine the roll, yaw and pitch angles of the platform, thus providing a measurement of geographic north. The processor also uses signals from a 3-component magnetometer on the platform to determine the magnetic north and thence the magnetic declination. A proton magnetometer is used to provide a check on the measurements of the 3-component magnetometer. Additionally, three single component magnetometers provide a measure of the local magnetic field gradient and serve to monitor artificially induced magnetic fields. An alternate embodiment of the invention uses at least three GPS receivers and may dispense with the 3-component of accelerometer to determine geographic north. Temporal local variations of the earth's magnetic field are tracked and used to correct conventional magnetic well surveys.