| Energy is the lifeblood of a country’s development.It is closely related to politics,economy and other aspects,and has a direct impact on the country’s stable development.Therefore,in order to enable the country to firmly grasp the right of self-energy security,it is very important to develop energy exploration and mining technology.With the development and application of electronic technology,the application of electronic technology in the field of petroleum and gas exploration and production should become the development trend of production technology.The increasingly complex downhole geological environment makes the requirements for the accuracy of borehole trajectory control increase day by day.Logging while drilling(LWD)technology can help ground operators understand the resistivity and other parameter information of downhole formation,so as to realize downhole geological guidance.The key of LWD technology is information transmission,including the information transmission between the measurement module near the drill bit and the MWD instrument above the screw,between the MWD instrument and the ground console.The wireless electromagnetic data transmission system designed in this paper is mainly used to realize the data information transmission between the measuring instrument while drilling near the drill bit and above the screw.Based on the implementation requirements of a LWD center project,a wireless data transmission system based on the principle of electromagnetic induction is designed in this thesis.The data transmission between the drill collar instrument near the drill bit and the other side of the drill collar can be realized.And the main functions of carrier signal generation,signal modulation,signal transmission,signal acquisition,signal demodulation and processing,as well as module communication,data storage and other auxiliary functions can be realized.The loop coil antenna is used to realize the electromagnetic coupling between the transmitting and receiving coils,so as to achieve the purpose of data transmission.The electromagnetic transmission theory,finite element simulation analysis,key technologies,software and hardware implementation and system testing are described in detail in this thesis.Based on the principle of electromagnetic induction,the basic theory of wireless data transmission is analyzed,and the attenuation characteristics of electromagnetic waves in lossless and lossy media are compared and analyzed.Combined with the propagation characteristics of electromagnetic wave in lossy medium,the overall scheme design of the system is completed from the analysis of system index.The finite element simulation model is established to analyze the influence of loop coil antenna on the transmission performance of electromagnetic signal and the attenuation characteristics of electromagnetic wave in the transmission process.Aiming at the anti-interference problem of signal transmission,the signal modulation and demodulation technology based on 2ASK is adopted;Aiming at the problem of weak signal acquisition,the signal extraction technology based on phase sensitive detection algorithm is adopted;A scheme based on FPGA and arm architecture is proposed to realize the system function;RS485communication is used to realize long-distance and stable data transmission between the system and the host computer or other main control boards.Finally,according to the technical indicators of the system,appropriate devices are selected for circuit design and the system prototype is welded.The preliminary test work is completed,including the single machine function test of the hardware circuit board and the ground system test,so as to complete the design and implementation of the wireless electromagnetic data transmission system. |
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