Research On Sound Field Characteristics Of Fractured Formation Based On Impulse Sound Source

With the continuous deepening of the exploration of oil and gas resources,the popular direction of the exploration field is moving closer to the dense and deep layers.Fractures often develop in tight lithologic formations such as carbonate rocks,igneous rocks and sandstones.Fractures can not only store oil and gas,but also provide a permeable channel to unexplored oil layers.Plasma impulse sound source is a high-power pulse sound source with wide spectrum coverage,high repetitive frequency and good safety.The Plasma impulse sound source's sound pressure level is much higher than the sound source used in logging.This paper uses plasma impulse sound source to detect fractured reservoirs,which solves the problem of limited detection depth of existing acoustic logging methods.This paper starting from the basic theory of sound field while drilling,analyzes the propagation process of impulse while drilling in the well,and derives the arrival formulas of various waves.Subsequently,the impulse sound field model was established on this basis,the acoustic field response characteristics of different sound source types,different sound source frequencies,and different formation types were compared and analyzed,the most suitable sound source parameters for detecting fractured reservoirs under drilling conditions was selected.Finally,the COMSOL finite element software was used to establish the impulse sound field model of the fractured formation in the case of hard formations,and the wave field characteristics and the amplitude of the Stoneley wave in the case of different fracture width,density,dip,longitudinal extension and radial extension were studied.The change law gives quantitative description of the development characterization parameters of fractured strata.The research results show that: at the same frequency,the sound pressure level of the impulse sound source up to 336dB,is far better than the Rick wavelet.When detecting target fractured reservoirs with a distance of more than 10m from the sound source,the detection effect of using reflected wave information is better than that of Lake wavelet.This conclusion deepens the understanding of the advantages of the impulse while drilling sound wave deep detection technology,and provides reference information for the expansion and application of this technology.