Research On The Electromagnetic Wave Resistivity Logging-while-drilling Technology Of Long Source Distance Drilling

The electromagnetic wave resistivity logging-while-drilling,as a part of logging technology,plays an indispensable role in the world logging industry.At the same time,as a key indicator to measure the performance of its instruments,the depth of detection has gradually received the attention of the world logging industry.From the current research situation,increasing the source distance is one of the effective methods to improve the depth of detection of the instrument.However,while increasing the source distance,the problem of severe attenuation of the received signal of the instrument will also follow.Therefore,under the premise of ensuring the received signal strength,the research on how to increase the source distance is carried out.The structure of the coil system of the traditional electromagnetic wave resistivity logging tool while drilling and its related theory are analyzed.On this basis,the resonance principle is introduced and the field coupling analysis is carried out.It finds out the method of increasing the source distance by making the coil resonance to improve the signal strength.In addition,it is found that the deviation of the resonant point of the structure has a great influence on the resonant effect.Therefore,a new type of the double-emission and single-receiving resonance coil system structure is proposed,and the simulation analysis is carried out.The results prove that this structure can not only has a more obvious effect on increasing the source distance,but also can avoid the disadvantages of the traditional coil system structure after the introduction of resonance.By constructing the resonant coil circuit model,the influence of the resonant coil parameters on the received signal is analyzed.Then,the influence of coil turns and frequency on the quality factor under different coil radius conditions and the influence of wire radius and coil radius on the quality factor under different coil turns are analyzed.Based on the analysis results,valid and economically reasonable parameters are determined,and subsequent experimental parameter selection is guided.The electromagnetic wave resistivity logging experimental platform while drilling is built,including the circuit part,the platform skeleton,the coil system part,the software system and the simulated stratum part.The detailed description of each part system is carried out.Based on the platform system,the experimental research is carried out.The experiment proves the disadvantages of the traditional coil system structure after the introduction of resonance.Then a new type of double-transmitter and single-receiver resonant coil system is made and its response characteristics is studied.The laboratory usually uses the scale ring to simulate the conductivity of the formation to study the response characteristics of the instrument.However,the calibration method of the double-emission and single-receiving resonance coil system is completely different from the traditional open-circuit coil system structure.Based on the geometric factor theory,the selection method of the scale ring parameters of the double-shot single-receiving coil type is studied.It is found that the relative smoothness and the scale ring resistance resolution should be considered in the parameter selection to reduce the measurement error.The experiment compares the open-circuit and resonance response characteristics of the receiving coil in a uniform formation,which shows that the resonance method only increases the amplitude of the receiving response without changing the amplitude ratio,and verifies the correctness of the calibration method of the scale ring.Further,the experiment shows the correctness of the double-emission and single-receiving coil system structure,and proves the effectiveness of the resonance method,which provides the possibility of increasing the source distance and increasing the depth of detection.