Laser Self-mixing Interferometric Vibration Measurements Method For Microscopic Residual Oil Dynamic

As a technology to improve oil recovery,ultrasonic oil recovery has attracted widespread attention from the industry because of its simple process,low cost,good applicability and no pollution to the reservoir.For the research on the mechanism of ultrasonic oil drive,although the stage results have been achieved in indoor experiments and field tests,there is a lack of in-depth research on the law of ultrasonic vibration on residual oil mobilization,specifically: Firstly,the influence of ultrasonic vibration on the stripping and transport capacity of microscopic residual oil in porous media is unclear.Secondly,the propagation and attenuation law of ultrasonic vibration in rock cores is unclear.To address the above problems,this paper carried out joint microscopic dynamic experiments of ultrasonic oil repelling,which includes observing the movement characteristics of different types of residual oil in porous media through microscopic visualization experiments of ultrasonic oil repelling at different amplitudes,detecting the vibration of oil droplets and water phases of residual oil at different locations and analyzes the vibration characteristics and vibration laws,designing and building a microscopic visualization experimental platform of ultrasonic oil repelling,which provides equipment support for real-time observation of the formation and distribution state of residual.The research was aimed at solving the problems of poor generality,low reconstruction efficiency,large measurement error and single measurement target in the field of vibration measurement,providing support for further research on the micro-mechanism of ultrasonic vibration on residual oil movement and vibration propagation law,the main research content is as follows.(1)Based on vibration theory,the equations of motion and ultrasonic equations of the particle units in the core under ultrasonic vibration were introduced,and the force conditions of the particle units in the rock core under ultrasonic vibration were given in conjunction with Newton’s second law.The results showed that the coercive motion of the core particles under ultrasonic vibration is consistent with the loading frequency,and the amplitude of the coercive motion of the particle units was proportional to the amplitude of the applied ultrasonic load.In addition,the forces on the unit particles within the core were significantly influenced by the amplitude of the ultrasonic waves.(2)Based on the equivalent Fabry-Perot(F-P)composite cavity model in the presence of optical feedback,the mechanism of laser self-mixing interference(SMI)effect was investigated.A multiple Hilbert transform phase deconvolution algorithm was proposed for the SMI signal with moderate feedback.The deconvolution algorithm of the multiple Hilbert transform phase was applied to different optical feedback mechanisms by means of a signal offset cancellation algorithm.The experimental results showed that the absolute error is 221 nm and the relative error was less than 4% for a C value of 4.6 under moderate feedback conditions.(3)To address the problems of large delay and low reconstruction efficiency of the traditional SMI displacement reconstruction algorithm under the weak feedback mechanism,a fast algorithm of reverse point detection was proposed.The method used the signal peak and valley value point detection technology to determine the laser SMI signal reversal point by applying the reversal point identification algorithm to the extracted peak and valley value points,and then used the half-stripe counting method to obtain the reconstructed vibration displacement for the problem of incomplete stripes at the reversal point.The experimental results showed that the absolute error of method was less than 20 nm,the relative error was less than 1%.(4)A Fourier transform-based main frequency harmonic order determination algorithm was proposed to address the problems of complex measurement structures and high measurement costs in the field of laser SMI multipoint vibration measurement.The improved algorithm solved the problem that the main frequency order algorithm cannot reconstruct two signals that are overlapped in the frequency domain.The experimental results showed that the Fourier transform main frequency harmonic order determination algorithm combined with the dual external cavity laser SMI model can detect two points of vibration information simultaneously by a set of devices.(5)This paper carried out ultrasonic oil repelling visualization experiments based on laser SMI,and improved the mechanism of ultrasonic oil repelling,concluding that ultrasonic waves can effectively act on membrane residual oil,corner residual oil and cluster residual oil,so that the membrane residual oil adsorbed on the rock surface,cluster residual oil and corner residual oil affected by liquid flow can be better used,and the free movement ability of oil-water emulsion could be improved.At the same time,oil,water and rock surface were interact with each other in the porous medium of the formation,and the time and amplitude of different types of residual oil were regular: blind end pore > throat channel > normal channel > cluster pore.Ultrasonic amplitude attenuation was an exponential function of propagation distance,and the amplitude of attenuation decreased with the increase of propagation distance.