Research On Methodology Of Drilling Acoustic Signal Detection Based On Duffing Oscillator

Acoustic signal detection technology while drilling has important theoretical significance and application value.Acoustic signal is under the influence of downhole noise in the process of signal transmission,which makes the ground receive the acoustic signal submerged in noise whose signal-to-noise ratio is extremely low.And the traditional detection method has high error rate when the input signal has low signal-to-noise ratio.Chaos theory,as a system of nonlinear science,has been very mature and perfect after decades of development since chaos phenomenon was first proposed.The application of chaos theory in weak signal detection has caused the attention of researchers,and has obtained some achievements.On the basis of these results,the paper takes up the research of practical use of chaos on drilling acoustic signal detection.With the drilling acoustic signal detection as the main topic of this paper,this paper studies the method of chaos theory applied to drilling acoustic signal.Chaotic system has characteristic of extreme sensitivity to initial parameters.Duffing system,as a classic chaos system,has this behavior without exception.The paper proposed the method of doffing system to detect the weak signal based on this feature.Paper's main work includes:(1)Paper firstly introduces the background and meaning of the acoustic signal transmission technology in oil drilling,then paper mainly introduces the present situation that chaos theory is applied to drilling acoustic signal detection.The chaotic theory is discussed systematically,which includes the chaotic signal processing methods and the characters of the chaotic system.Then the paper analyzes and describes the various characteristic parameters of chaotic system.(2)At first of all,dynamic behavior of Duffing oscillator is analyzed theoretically and numerically,upon which the majority of this work is founded.Then the paper studied weak signal detection method based on the chaos critical state of Duffing oscillator.Based on that,the paper studied 2FSK signal detection method system based on Duffing oscillator and build a 2FSK signal detection system also based on Duffing oscillator.Finally we solve the problemthat the test signal and the drive signal have different phase.(3)This paper analyses the downhole acoustic frequency characteristics of the transmission channel and handles channel model.Then the Duffing system detects 2FSK signal after channel.(4)The paper finally explores the method of hardware realization of Duffing system,respectively on the analog circuit and DSP.By comparing the advantages and disadvantages of them,it illustrates the feasibility of designing weak signal detector with DSP as core device in the future.