Research On Acquisition Control And Transmission Circuit Of Seismo-electric Logging In Wellhole

With the rapid growth of the global economy,the demand for energy in countries is increasing,and the consumption of oil is on the rise.How to detect and exploit oil accurately and efficiently has become the focus of increasing attention of all countries.In oil exploration,the seismo-electric logging technology based on the seismo-electric effect has been hot in recent years..A double electric layer structure is formed in porous media containing fluid,the positive and negative ions are adsorbed on both sides of the solidliquid interface,when the electric double layer is subjected to the external vibration,the positive and negative ions will produce relative displacement and radiate out the electromagnetic field,which is the seismo-electric effect.Seismo-electric logging is the acquisition of the seismo-electric signal.By analyzing the seismo-electric signal,some parameters of the formation can be obtained,these parameters can be used as an important basis for judging the existence of oil.Seismo-electric signal is very weak,which is usually drowned by background noise,therefore,designing a system that can collect seismoelectric signal becomes the ultimate goal of researchers in the industry.With the background of the existing results of seismo-electric logging technology,this thesis designed the acquisition control and transmission circuit of the wellhole.The main method is to use FPGA as the main control unit of the acquisition control and transmission circuit to control 16 bits ADC acquisition and processing of seismo-electric signal,seismo-electric signal is sent to FPGA internal storage and cumulative average.The data of the eight acquisition control circuits are uploaded to the transmission control circuit through the SPI bus,and then uploaded to the host computer through UART protocol to display the waveform of the seismic signal in real time.At last,the time velocity correlation method is used to deal with the seismo-electric signal to extract the velocity of sonic wave propagating along different media.This thesis first completed the design of the transmission control hardware circuit,including FPGA peripheral circuit design,differential to single circuit design,digital isolation circuit design,communication interface circuit design,power management circuit and PCB design.Secondly,this thesis completed the logic design and function simulation of the acquisition control and transmission control circuit.We design clock division frequency,ADC control,FSM state machine,accumulative averaging and data transmission module using Verilog HDL language.At last,this thesis completed the programming of the host computer software that can display the eight-way seismoelectric signal in real time,and completed the development the time velocity correlation method which can extract the velocity of sonic wave.Through joint debugging of hardware and software system,the performance and function of each module of the system are tested,and the actual acquisition of seismoelectric signal is carried out by simulation experiment.Finally,the system designed in this thesis realized the acquisition and real-time display of eight-way seismo-electric signals,and successfully extracted the velocity of sonic wave through time velocity correlation algorithm,which met the design requirements and achieved the expected performance.