| Non-renewable resources such as coal,crude oil,natural gas,and oil shale are of great significance to human production and life.When mining these non-renewable resources,detection technology is particularly important.The use of advanced detection technology is conducive to reducing exploration costs and discovering oil and gas resources more efficiently.In the exploration of underground resources,the electromagnetic wave transmission technology while drilling is one of the focuses in the current research.Due to the transmission characteristics of electromagnetic waves in the stratum,the attenuation of electromagnetic waves is significantly different from that in the air.Therefore,high-frequency electromagnetic waves are basically difficult to use in the transmission system where the medium is the formation.Due to the attenuation characteristics and the large noise of the actual drilling platform,low-frequency signals are less likely to be submerged by noise than high-frequency signals in the formation.However,extremely low frequency transmission also brings the disadvantage of low transmission efficiency.Too low efficiency may lead to failure to achieve the purpose of real-time monitoring of exploration information.Therefore,how to ensure the efficiency of information transmission in the case of using extremely low frequency signals is one of the difficulties of this subject.After comparing and analyzing several modulation schemes,carrying out simulation analysis,the FSK scheme is selected as the modulation method in the system from the modulation schemes such as ASK,BPSK,FSK,etc.Based on the simulation of the communication principle,the relevant technical design scheme is proposed,and then the relevant scheme is analyzed and explained in principle.Based on the implementation principle in the proposed transmitter,the core chip of the MSP430F169 chip crop transmitter circuit is used to complete the coding and modulation of the FSK signal.In the ground receiver,the synchronization and demodulation of the FSK signal is completed based on the DFT-related algorithm Operation,the preparation of the receiving signal processing program is completed.Finally,the upper computer completes the requirements for real-time monitoring of data.After the simulation test in the laboratory,the transmission experiment of the actual drilling platform was finally completed.The transmission test with a depth of 1000 meters was completed,which verified the reliability and stability of the wireless electromagnetic wave transmission system while drilling.The research results of this subject provide a good technical foundation for the follow-up improvement of the technology while drilling. |
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