Attitude Measurement And Correction Of Downhole Tool Based On MEMS Technology

At present,Chinese petroleum is characterized by high import dependency,and petroleum security situation is very stern.Most undeveloped petroleum and gas resources locate in unconventional areas,such as the low permeable block,deep formation and marine area.Steering drilling technology is the highest level in the current petroleum drilling technologies and results in the 4th world's petroleum technology revolution,which may change the global energy structure.Developing the steering drilling technology is very necessary for our country.Accelerometers are adopted as the attitude measurement sensors to acquire the attitude parameters of the drilling tool in the designed control system.In the orthogonal coordinate system,the installation position errors lead to the nonlinear errors of the sensor's three-axis output signals while manufacturing,machining,installation and quadratic integration.This influence the measurement accuracy significantly.Therefore,the focus of the full-bore steering drilling is to accurately measure the downhole attitude parameters,such as the deviation angle I,the tool face angle T and the azimuth A.In the rotary modulation steering drilling system,the international researches on attitude measurement technology are investigated in this thesis.Three orthogonal accelerometers are used as the sensors to realize the attitude measurement of drilling tools.Theoretical analysis of the position errors originating from the nonorthogonality,misalignment,installation and integration are emphatically analyzed.Based on the independent theory for each axis,three virtual orthogonal coordinate systems are established and the nonorthogonal position error models are derived.Conventional correction method for position errors are studied,in which the effect of the numerical accuracy of the correction matrix are analyzed.The method of balanced compensation is put forward.Comparison test between the proposed and conventional compensation is realized with the TX-3S inclinometer.Results indicate that the measurement accuracy of the position parameters of the downhole tools based on dual-axis accelerometer ADXL206 meets the local requirement.Due to the error compensation of the nonorthogonal,the balanced compensation eliminates the periodic system errors which occurs in conventional compensation.Compared with conventional compensation,the accuracy of the proposed method is also significantly improved.