| Oil drilling technology developed rapidly, the drilling engineering develops into automation and information aspects[1], that requires the data collected by the underground drilling equipments during the drilling process to be transmitted to the ground in real-time, but in present, the major Drilling Date Transmission (DDT) cannot meet the requirement. Entering 21 century, new Drilling Date Transmission (DDT) used in the Logging While Drilling (LWD) was available in the foreign country. The data transmission system IntelliPipe which developed by the IntelliServ, based on the principle of electromagnetic induction coupling, the transmission rate can reach 2Mbps. The electromagnetic induction coupler is installed in the Drill pipe joints, It achieved non-contact signal transmission and can transmission signal with extremely high rate, breaks the bottleneck of data transmission in the drilling.In this disertation, with the knowledge of IntelliPipe developed by IntelliServ and on the basis of experimental system established by previous senior, I improved the circuit model of single induction coupler and measured the model parameter. On that basis, the new circuit model of the electromagnetic transmission channel is established. Simulation by PSPICE software is compared with the actual test to verify the accuracy of the channel model. Various characteristics of the transmission channel of magnetic induction can be obtained by the simulation of the model using the software. This disertation gives the frequency characteristics of signal transmission, and the choice of the frequency for the communication signal is also provided.Because of the frequency characteristics of the transmission channel, The carrier frequency is the only one factor that is not changed obviously after pass the transmission channel, and the Frequency Shift Keying (FSK) is easy to achieve. So in this disertation, Frequency Shift Keying (FSK) is chosen as the digital modulation and demodulation method. A modem circuit is designed based on AD9832 and a Demodulating circuit based on XR2211, and the software and algorithms of the modem is written. The stability of the data rate is 57.6 kbps, the transmission distance has reached 250m, compared with the previous experimental system. The transmission distance has been improved and reliable real-time data transmission is available in the channel.Finally the experimental system of electromagnetic induction transmission is established. The system composed of 26 coupler and 25 simulated drill pipe. The results of the transmission experiment show that the system is of practical value. bit error rate is less than 10-7. |
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