Analog Decoupling And Calculation Of Downhole Tool Attitude Measurement

It is very important to measure the accurate borehole trajectory parameters near the drill bit in real time.In order to obtain the high precision posture parameters of the inclination angle and tool face angle and the effective control of well trajectory,a kind of sensor which consists of accelerometer and flux gate or gyroscope is adopted.First,the triangle function relationship between the sensor outputs and the posture parameters is derived.And the formulas are used to calculate the inclination angle and the tool face angle are given.With the AD639,a high-precision function generator,and AD734,an analog 4-Quadrant Multiplier/Divider,a kind of divider circuit is designed to decouple and calculate the tool face angle.Under fixed and variable inclination,the circuit system is tested and data errors are analyzed.When the fixed well inclination is 45°,the minimum error is 0.0098°,and the average error is 0.1742°.In the well inclination between 0 to 90°the minimum error is 0.096°,and average error is 0.2543°,the maximum error is less than 0.5 °.The test data show that the calculation method is feasible,and the precision of the test circuit meets the told requirements.This method can be used to implement the decoupling and calculation of the posture measurement for downhole tool.