Study On The Suppression Effect Of Composite Structured Sound Isolators On Drill Collar Waves In Deep Detection Of Impulsive Sound Sources

In this thesis,we propose a composite structure acoustic isolator for deep detection of downhole impulsive sound sources.The isolator structure is designed to suppress the drill collar waves by carving the groove on the outer surface of the drill collar and embedding a material with a large difference in acoustic impedance to the inner wall of the drill collar.ANSYS finite element software was used to simulate the mechanics,acoustics,and fluid-solid coupling of the sound field of the composite structural sound insulation.In the mechanical characterization stage,the eight parameters of outer groove spacing,outer groove width,outer groove depth,outer groove transition arc radius,inner groove width,inner groove depth,inner groove transition arc radius and number of inner grooves are analyzed for their effects on the mechanical properties of the sound insulation body,and finally a suitable parameter range is selected and fatigue life is estimated,and the final mechanical verification results meet the drilling collar strength required by the actual working conditions.In the acoustic characteristics research stage,the sound insulation principle of the composite structure sound insulation body was firstly introduced,and then establishment of a drill collar without groove structure and verification of the correctness of the calculation method by ANSYS simulation,and then the acoustic characteristics of the composite structure sound insulation body were analyzed for the deep detection of the impulsive sound source,mainly includes the influence of different embedding materials and six parameters of outer groove width and spacing,outer groove transition arc radius,inner groove width,inner groove transition arc radius and number of inner grooves on the sound insulation effect of composite structure sound insulation body,the results show that among the three embedded materials,rubber has the best attenuation effect on the drill collar wave;the larger the width and spacing of the outer slot,the smaller the attenuation of the drill collar wave,but the amount of time delay increases;the larger the radius of the outer slot transition circle,the smaller the attenuation of the drill collar wave,and the amount of time delay is basically unchanged;the larger the width of the inner slot,the better the sound insulation effect of the sound insulation body,but the amount of time delay is basically unchanged;the larger the radius of the inner slot transition circle,the smaller the attenuation of the drill collar wave,and the amount of time delay is basically unaffected;the larger the number of inner slots,the better the sound insulation effect of the sound insulation body,and the amount of time delay also tends to increase slowly.In the sound field fluid-solid coupling analysis stage,the attenuation effect of drill collar wave in mud medium and air medium and the attenuation effect of drill collar wave in different density mud environment were mainly analyzed,the analysis results show that the attenuation effect of drill collar wave in mud medium is better than that in air medium,and the change of mud density has less effect on the sound insulation and time delay of the sound insulation body,but considering that a denser mud will increase the signal-to-noise ratio of stratigraphic longitudinal waves,a denser mud can be selected according to the need in the actual drilling operation.