Research And Design On Wireless Electromagnetic Short-hop Transmission System Of Down-hole Near-bit Data

With the development of electrical technologies,measurement-while-drilling(MWD)technology has become more and more mature.In the last several decades of years,the drill of ultra-thin reservoir and fault block oil reservoirs is already booming and the demand of controlling accuracy is becoming higher than ever before.So in this case,the near-bit data is becoming more and more important.However due to the down-hole motor,the transmission between near-bit data and MWD system can’t use wire,so the research.of wireless short-transmission system of near-bit data supplies both theoretical value and practical significance.With research of the new developments in the art,this thesis uses electromagnetic wave to transfer the information,and finite element method is applied to the short-hop system to achieve the pattern of down-hole electromagnetic wave transmission.The transmitting and receiving circuit is also designed and experimented in this thesis.The main work of this thesis is as follows:Firstly,this thesis builds the transmission model of down-hole wireless electromagnetic short-hop signal,and the spiral coil and the magnetic core circuit are theoretically analyzed.Based on the battery voltage of down-hole system and signal frequency,the parameter and material of magnetic core and spiral coil is selected and calculated.Through this,on the promise of system’s stabilization,the utilization rate of the power supply is maximized.Secondly,this thesis builds the transmission model of down-hole wireless electromagnetic short-hop system.With infinite element theory this thesis lays special stress on analyzing the chief factors of frequency、electrical resistivity and the length between the two coils to provide data support for the design and selection of the circuit system.Finally,this thesis Designs and Implements the down-hole communication circuit.Referring to the propagation characteristic of electromagnetic wave and complex down-hole environment this thesis chooses reasonable data signal modulation type and use AD9833 to design the 2FSK modulation circuit with ARDUINO NANO as control chip,and we also use NE564 to design the demodulation circuit.Then the transmitting and receiving circuit are both tested and verified by experiments.Through this we may lay a foundation for the next step of the research.