Research On The High Resolution Micro-resistivity Imaging Logging Acquisition Circuit

In recent years,in the oil drilling detection system,the technology of transmitting the underground geological reservoir information to the surface and displaying it in real time has become the focus of analysis and research.Coupling communication transmission system is a downhole communication system developed and designed for the transmission of information between the stator and rotor in the relative rotation of oil drilling tools.In recent years,the electromagnetic measurement while drilling(MWD)transmission system has become the key research direction of oil exploration.On the one hand,in the electromagnetic MWD transmission system,the complex and bad downhole environment and the large background noise between drill strings cause the great interference between codes.On the other hand,the transmission frequency band is very narrow,and the transmission process time delay is large.These constraints seriously restrict the downhole transmission system,so the stability,reliability and efficiency of the downhole transmission system has become the main design points.The goal was to design a stable,reliable information transmission system that would allow two-way communication between the surface system and the downhole.This project uses the loose coupler to complete the wireless transmission of data stream.From the point of view of the field engineering work,the main modules such as the relevant signal transmitter,matching circuit and receiver are designed to realize the analog demodulation.In addition,on the basis of analog demodulation,this paper proposes a new demodulation scheme to solve the problem that the coupled communication circuit has high error code and is vulnerable to strong electromagnetic interference.By adding digital demodulation module,the anti-interference ability and reliability of the demodulation scheme are increased.Digital demodulation part is based on FPGA and AD chip,AD sampling is used for analog-to-digital conversion,and then M sequence detection is carried out by FPGA to get baseband signal,which is transmitted to PC display through serial port RS485.The prototype can effectively increase the anti-jamming ability of the information and further improve the stability and reliability of the system transmission.In this thesis,the transmitting and receiving module of the signal are tested and designed,and the resonant circuit module is calculated theoretically.The final experimental results verify that the loose coupling wireless signal communication system has the characteristics of high temperature resistance of 150? and anti-interference.