Application Of Weak Signal Detection Technology In Lateral Logging

With the ever-increasing detecting depths, the appearance to drilling fluid invasion of formation becomes more and more complex, the dual lateral logging tool provides only two modes of apparent resistivity curve, which is unable to meet the needs of the complex oil and gas evaluation. The development of a new type array lateral logging tool supporting multiple detection mode is imperative. According to the simulation results, the minimum voltage detected by the underground supervision electrode which with large dynamic range is only several hundred nanovolts. Thus, in order to improve the accuracy of detection, it is necessary to study on the application of weak signal detection technology in lateral logging.In this paper, the array lateral logging weak signal detection techniques have been studied. By studying the work mode of array lateral logging, on the basis of analyzing the characteristics of signals in lateral logging, the corresponding design scheme of detection system is put forward, including hardware design and the determination of digital signal processing key techniques. In the hardware part, First, the index of the design parameters is determined, and the key part is the design of signal processing circuitry, including the design of low-noise preamplifier, selection of the structure and parameters of the filter, and Multisim simulation and analysis. The emphasis of digital signal processing is on the selection of schemes. In the Matlab simulation environment, the results of comparison between de-noising results of digital filter and wavelet transform shows that the latter is better. And by comparing to the FFT algorithm and digital phase-sensitive detection algorithm, it is found that the latter has higher detection accuracy, and smaller errors. Finally, through the comparative analysis of relative error of the wavelet de-noising with digital phase-sensitive detection and the direct digital phase-sensitive detection, and from the timeliness and concise design considerations, the latter is selected, and the digital signal processing flow chart is designed. And then, the function of signal pre-printed circuit board is tested, which shows that its experimental results is able to meet the expected design target.