Directional Sensors

The Directional Sensor is made up of electronic printed circuit boards, a Tensor Tri-Axial Magnetometer and a Tensor Tri-Axial Accelerometers, and Temperature sensor. These modules are configured into a directional probe and are run in the field mounted in a nonmagnetic drill collar. The Directional Sensor provides measurements which are used to determine the orientation of the drill string at the location of the sensor assembly.

The Directional Sensor measures three orthogonal axis of magnetic bearing, three orthogonal axis of inclination and instrument temperature. These measurements are processed and transmitted by the pulser to the surface. The surface computer then uses this data to calculate parameters such as inclination, azimuth, high-side toolface, and magnetic toolface.

The sensor axes are not perfectly orthogonal and are not perfectly aligned, therefore, compensation of the measured values for known misalignments are required in order to provide perfectly orthogonal values. The exact electronic sensitivity, scale factor and bias, for each sensor axis is uniquely a function of the local sensor temperature. Therefore, the raw sensor outputs must be adjusted for thermal effects on bias and scale factor. Orthogonal misalignment angles are used with the thermally compensated bias and scale factors to determine the compensated sensor values required for computation of precise directional parameters.

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