| Logging while drilling technology can acquire geological parameters that have not been eroded by mud media pollution by placing multiple sensors close to the bit and continuously detecting formation information at the drilling hole or bit during the drilling process.One of the difficulties of logging while drilling technology is to transfer the information collected at the bit to the logging while drilling system by bypassing the transmission motor.Cable transmission channel is easy to be damaged-which can't guarantee the stability of data transmission.Wireless transmission mode can obtain better transmission quality.However,the transmission efficiency of different wireless transmission modes is greatly affected by the underground formation environment,and the transmission efficiency can't be guaranteed.Therefore,in order to improve the stability of near-bit signal transmission,it is important to study the transmission characteristics of wireless short transmission technology with transceiver coil and wireless short transmission technology of electric signal in different underground media for improving the transmission quality of near-bit signal.This paper mainly studies the basic principles of wireless short transmission technology of transceiver coil and wireless short transmission technology of electric signal,constructs two transmission system models,carries out finite element simulation,obtains the signal transmission rules and applicable conditions of two kinds of short transmission technology under different geological conditions,and carries out ground test of wireless short transmission technology of transceiver coil.The main work includes:Based on the basic theory of electromagnetic field,the characteristics of electromagnetic parameters and attenuation characteristics of electromagnetic wave in different media are analyzed.The basic principle of transceiver coil transmission is studied,the model of transceiver coil transmission system is constructed,and the magnetic ring material of the coil is determined.The basic principle of wireless short transmission of electric signal is studied,and its equivalent circuit is analyzed.According to the condition of underground equipment,the size of transceiver coil is designed,the number of?winding turns of transceiver coil is calculated,the model of short transmission system of transceiver coil is constructed.and the finite element simulation is carried out.The influence of transmission frequency,dielectric conductivity and transmission distance on the received signal is studied.It is found that the transmission quality of the signal is better when the transmission frequency is about 15KHz.The simulation of wireless short transmission system of electric signal is carried out.The influence of transmission distance,transmission frequency and dielectric conductivity on the received signal is analyzed.It is found that the receiving quality of the signal is better when transmission frequency is lower than 25Hz.By comparing the simulation results of the two wireless short transmission technologies.when the conductivity of the medium is lower than 5S/m,better reception quality can be obtained by using transceiver coil transmission mode,while in the medium with conductivity higher than SS/m,better reception quality can be obtained by using electrical signal transmission mode.Through E5810A gateway,the wireless short transmission test system is built,and the control interface of the test system is developed,and the ground test of the wireless short transmission technology of transceiver coil is carried out.The experimental analysis shows that the power of the received signal increases with the increase of the transmitting power and decreases with the increase of the coil distance.In the frequency range of 15KHz-20KHz,the power and phase of the received signal are relatively stable.which is an ideal transmission frequency band.Through the simulation and experiment of wireless transmission of transceiver coil and electric signal.the transmission characteristics and frequency of two kinds of wireless transmission technology in different media are obtained.The high-efficiency transmission of signals under the condition of large variation of electric conductivity is realized,more accurate geological information is obtained,and the success rate of logging while drilling is improved. |
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