Design Of Complex Resistivity Logging Instrument

China is a big country of mineral resources,but because of the deep burial of mineral resources,the difficulty of observation has always been a hindrance to the development of resources.In order to understand the distribution of underground material structure,it is necessary to drill from the surface to the underground,and use logging equipment to measure from the wellhead to the underground.This method of drilling measurement is called geophysical logging,or logging for short.Logging has become an important means of mineral resources development and engineering exploration since its birth.With the increasing development of mineral resources year by year,the requirement for logging has been constantly improved.Resistivity method,as the most commonly used method in electrical logging,has also attracted more and more attention.Complex resistivity method is a new method to analyze resistivity in frequency domain.It can obtain capacitance information besides impedance information,which can greatly improve the accuracy of judgment.At present,the theoretical research on complex resistivity logging in China is gradually maturing,but the design of related instruments is still relatively small,so it is necessary to study the design of complex resistivity logging tools.Based on the principle of complex resistivity logging,a complex resistivity logging tool is designed in this paper.The real and imaginary parts of complex resistivity can be obtained by collecting the current signals of transmitting electrodes and the voltage difference signals between receiving electrodes.Before the design,the feasibility of this method is confirmed by simulation with MATLAB/Simulink.Then the hardware circuit is designed according to the principle,which mainly includes two parts: the transmitting system and the receiving system.In order to improve the stability of the power supply,a power module with stable output current and continuously adjustable voltage is used in the transmitting system.The Hall current sensor and H bridge are combined to generate and measure the alternating current signal.Aiming at the problem of H-bridge driving and weak current protection,an isolation driving circuit is designed by using 6N137 photoelectric coupler,which isolates the strong current from the weak current while realizing H-bridge driving.Receiving system is used to collect the current and voltage difference signal.For this reason,a conditioning circuit is designed to filter and amplify the initial signal.Combining with ADS1256 chip,a data acquisition circuit with ARM microcontroller as the control core is designed,which effectively guarantees the accuracy of data acquisition.At the same time,the digital phase-sensitive detector is designed by using computer and digital technology,and the correlation detection of frequency domain signal is realized.In addition,using virtual instrument technology and wireless transmission means,using computer and software to replace most of the physical devices,and using WiFi module to replace the connection line,solve the instrumentation instability,power consumption and heavy problems.In order to ensure the synchronization of data acquisition in receiving system and transmitting signal in transmitting system,synchronization signal is used to connect the two and combine them as an integrated transmitter and receiver.The software design includes the program design of ARM microcontroller and the software design of host computer.The program of ARM microcontroller is developed based on C language.It is used to control ADC chip for data acquisition and H-bridge driving signal generation.The software of host computer is designed by LabVIEW to realize signal parameter setting,instrument operation control and data processing and preservation.After the instrument is designed and assembled,in order to verify the performance of the prototype and the accuracy of the measured data,the laboratory device is used to build a model and carry out signal transmission and test of the whole machine.Through collecting and analyzing the data,effective conclusions are drawn.