Research On Signal Acquisition And Processing Based On Seismoelectric Logging

With the rapid development of today's society,the demand for energy in all walks of life is also increasing.As one of the most important resources,petroleum resources have received the attention of various countries;how to explore and exploit petroleum resources has always been the research focus of various countries.Since Thompson discovered the existence of seismo-electric signals in experiments in 1936,the seismoelectric effect has gradually become a research hotspot in underground resource exploration.Seismo-electric logging detects electromagnetic signals compared with sonic logging.The wave influence is small,so it shows the potential for geological exploration.However,the seismo-electric signal excited by sound waves is generally weak,and the signal amplitude can reflect the measured porosity of the environment to a certain extent.Therefore,how to receive seismo-electric signals has become an urgent problem to be solved.The main research content of this thesis is to design a set of seismo-electric signal acquisition and signal processing system.Aiming at the collection and processing of weak seismo-electric signals,the innovative work of this thesis includes:(a)Propose and design wavelet denoising and related detection to process seismo-electric signals and use slowness-time coherence method to extract wave speeds.After simulation testing and experimental verification,the post-processing results of several methods can effectively extract the wave speed and reduce the noise interference,and solve the problem that the wave speed is difficult to be extracted due to the poor signal-to-noise ratio of the seismoelectric signal.(b)The acquisition and transmission circuit is designed with FPGA chip as the control core,and the signal processing is implemented in the hardware circuit,including numerical filtering and related convolution processing,so as to suppress the interference noise of the signal as much as possible.(c)The seismo-electric experiment test environment was built,the seismo-electric signals were collected,and the above signal processing methods were used to process the signals.The results show that the signal-noise ratio after processing has been significantly improved.Effectively extract the wave speed corresponding to the seismo-electric signal.Finally,after completing all the designs,the entire system is debugged jointly with software and hardware,and the system is tested in a laboratory environment after confirming that the system is working properly.In the laboratory,the U-shaped rock trough is used to simulate the underground wellbore environment to test large porosity rock samples.The test results show that all parts of the entire system are working normally.Compared with the initial results,the results after processing by the signal processing method selected in this article can more clearly distinguish the wave speed and delay,which meets the analysis requirements.