Unlike the real-valued plane wave reflection coefficient(PRC)at the pre-critical incident angles,the frequency-and depth-dependent spherical-wave reflection coefficient(SRC)is more accurate and always a complex value,...Unlike the real-valued plane wave reflection coefficient(PRC)at the pre-critical incident angles,the frequency-and depth-dependent spherical-wave reflection coefficient(SRC)is more accurate and always a complex value,which contains more reflection amplitude and phase information.In near field,the imaginary part of complex SRC(phase)cannot be ignored,but it is rarely considered in seismic inversion.To promote the practical application of spherical-wave seismic inversion,a novel spherical-wave inversion strategy is implemented.The complex-valued spherical-wave synthetic seismograms can be obtained by using a simple harmonic superposition model.It is assumed that geophone can only record the real part of complex-valued seismogram.The imaginary part can be further obtained by the Hilbert transform operator.We also propose the concept of complex spherical-wave elastic impedance(EI)and the complex spherical-wave EI equation.Finally,a novel complex spherical-wave EI inversion approach is proposed,which can fully use the reflection information of amplitude,phase,and frequency.With the inverted complex spherical-wave EI,the velocities and density can be further extracted.Synthetic data and field data examples show that the elastic parameters can be reasonably estimated,which illustrate the potential of our spherical-wave inversion approach in practical applications.展开更多
The propagation characteristics of impact waves across a planar interface between a ceramic layer and a ceramic/metal(C/M) composite layer were investigated. Two interfacial boundary conditions were considered: one wa...The propagation characteristics of impact waves across a planar interface between a ceramic layer and a ceramic/metal(C/M) composite layer were investigated. Two interfacial boundary conditions were considered: one was a shear coupling boundary condition that simulated a perfectly bonded interface between the ceramic and composite, and the other was a slip boundary condition that only allowed a transmission of the transverse motion and normal stress at the interface. The ceramic was subjected to an incident impact wave. The ceramic and composite was assumed to be elastic during impact. The study was based on a basic method provided by Furlong, Westburg and Phillips for predicting the reflection and refraction of spherical waves across a planar interface separating two elastic solids. Emphasis was put on the effect of the metal volume fraction in the composite, ceramic thickness and interfacial boundary condition on the reflected waves. New and interesting results are obtained that provide a very useful guidance for design of a ceramic/composite armor and of a C/M functionally graded appliqué.展开更多
Acoustic reflection imaging logging technology can detect and evaluate the development of reflection anomalies,such as fractures,caves and faults,within a range of tens of meters from the wellbore,greatly expanding th...Acoustic reflection imaging logging technology can detect and evaluate the development of reflection anomalies,such as fractures,caves and faults,within a range of tens of meters from the wellbore,greatly expanding the application scope of well logging technology.This article reviews the development history of the technology and focuses on introducing key methods,software,and on-site applications of acoustic reflection imaging logging technology.Based on the analyses of major challenges faced by existing technologies,and in conjunction with the practical production requirements of oilfields,the further development directions of acoustic reflection imaging logging are proposed.Following the current approach that utilizes the reflection coefficients,derived from the computation of acoustic slowness and density,to perform seismic inversion constrained by well logging,the next frontier is to directly establish the forward and inverse relationships between the downhole measured reflection waves and the surface seismic reflection waves.It is essential to advance research in imaging of fractures within shale reservoirs,the assessment of hydraulic fracturing effectiveness,the study of geosteering while drilling,and the innovation in instruments of acoustic reflection imaging logging technology.展开更多
Linearized approximations of reflection and transmission coefficients set a foundation for amplitude versus offset（AVO） analysis and inversion in exploration geophysics.However,the weak properties contrast hypothesi...Linearized approximations of reflection and transmission coefficients set a foundation for amplitude versus offset（AVO） analysis and inversion in exploration geophysics.However,the weak properties contrast hypothesis of those linearized approximate equations leads to big errors when the two media across the interface vary dramatically.To extend the application of AVO analysis and inversion to high contrast between the properties of the two layers,we derive a novel nonlinearized high-contrast approximation of the PP-wave reflection coefficient,which establishes the direct relationship between PPwave reflection coefficient and P-wave velocities,S-wave velocities and densities across the interface.（A PP wave is a reflected compressional wave from an incident compressional wave（P-wave）.） This novel approximation is derived from the exact reflection coefficient equation with Taylor expansion for the incident angle.Model tests demonstrate that,compared with the reflection coefficients of the linearized approximations,the reflection coefficients of the novel nonlinearized approximate equation agree with those of the exact PP equation better for a high contrast interface with a moderate incident angle.Furthermore,we introduce a nonlinear direct inversion method utilizing the novel reflection coefficient equation as forward solver,to implement the direct inversion for the six parameters including P-wave velocities,S-wave velocities,and densities in the upper and lower layers across the interface.This nonlinear inversion algorithm is able to estimate the inverse of the nonlinear function in terms of model parameters directly rather than in a conventional optimization way.Three examples verified the feasibility and suitability of this novel approximation for a high contrast interface,and we still could estimate the six parameters across the interface reasonably when the parameters in both media across the interface vary about 50%.展开更多
A new method is developed to constrain S-wave velocity structures of the shallow crust based on frequencydependent amplitudes of direct P-waves in P-wave receiver functions(P-RFs). This method involves the following t...A new method is developed to constrain S-wave velocity structures of the shallow crust based on frequencydependent amplitudes of direct P-waves in P-wave receiver functions(P-RFs). This method involves the following two steps:first, the high-frequency approximate amplitude formula of direct P-waves in P-RFs of individual stations is used to fit the observed amplitude distribution against the ray parameters at different frequencies, and second, the S-wave velocity depth profile beneath each station is constrained according to an empirical correlation between frequency and depth. Unlike traditional inversion techniques, the newly developed method is not dependent on initial velocity models, and the lateral and vertical resolutions of the results are controlled by the interstation distance and the data frequency, respectively. The effectiveness of the method is verified by synthetic tests on various models. The method is then applied to teleseismic P-RF data from a NW-SEtrending linear seismic array extending from the northeastern Tibetan Plateau to the central Sichuan Basin to construct an S-wave velocity image of the shallow crust along the array. The imaged velocity structure is further analysed and compared with the regional geology. In particular, the structural differences of sedimentary basins in the cratonic area of the stable Sichuan Basin and tectonically active belts in northeastern Tibet are investigated. By combining our results with previous observations, the relationship between the surficial geology and deep processes in the study region is also discussed.展开更多
Understanding the acoustic characteristics of hydrates in various sediments is crucial for hydrate resource detection and safe and efficient exploitation,as hydrate occurrence patterns vary greatly in different sedime...Understanding the acoustic characteristics of hydrates in various sediments is crucial for hydrate resource detection and safe and efficient exploitation,as hydrate occurrence patterns vary greatly in different sediments.In this work,sediments with different bentonite contents,water saturations,and types were prepared to investigate the characteristics of P-wave velocity(reflecting the magnitude of hydrate saturation in the sediment)and amplitude(reflecting the degree of hydrate-sediment cementation)during hydrate formation and depressurization.During hydrate formation,the P-wave velocity and amplitude have similar trends.As clay content increases,the P-wave velocity increase rates quickened.On the other hand,the increased rate of P-wave velocity slows down with the increase of water saturation in the clay-bearing sediments.Comparing various types of sediment shows that the water absorption and swelling of bentonite reduce the pore space,speeding up the cementation of the hydrate with the sediment and increasing P-wave velocity at a faster rate.Correspondence between P-wave velocity and hydrate saturation is strongly related to sediment type,clay content,and water saturation.The rapidly decreasing amplitude in the early stage of hydrate depressurization indicates that hydrate in clay-bearing sediments is weakly cemented to the sediments,which is prone to stratigraphic instability.The findings of this study offer guidance for hydrate resource assessments in clay-bearing sediments as well as geologic risk estimations during hydrate mining.展开更多
The water-lubricated thrust bearings of the marine rim-driven thruster(RDT)are usually composed of polymer composites,which are prone to serious wear under harsh working conditions.Ultrasonic is an excellent non-destr...The water-lubricated thrust bearings of the marine rim-driven thruster(RDT)are usually composed of polymer composites,which are prone to serious wear under harsh working conditions.Ultrasonic is an excellent non-destructive monitoring technology,but polymer materials are characterized by viscoelasticity,heterogeneity,and large acoustic attenuation,making it challenging to extract ultrasonic echo signals.Therefore,this paper proposes a wear monitoring method based on the amplitude spectrum of the ultrasonic reflection coefficient.The effects of bearing parameters,objective function,and algorithm parameters on the identification results are simulated and analyzed.Taking the correlation coefficient and root mean square error as the matching parameters,the thickness,sound velocity,density,and attenuation factor of the bearing are inversed simultaneously by utilizing the differential evolution algorithm(DEA),and the wear measurement system is constructed.In order to verify the identification accuracy of this method,an accelerated wear test under heavy load was executed on a multi-functional vertical water lubrication test rig with poly-ether-etherketone(PEEK)fixed pad and stainless-steel thrust collar as the object.The thickness of pad was measured using the high-precision spiral micrometer and ultrasonic testing system,respectively.Ultimately,the results demonstrate that the thickness identification error of this method is approximately 1%,and in-situ monitoring ability will be realized in the future,which is of great significance to the life prediction of bearings.展开更多
基金the sponsorship of the Marine S&T Fund of Shandong Province for Pilot National Laboratory for Marine Science and Technology(Qingdao)(Grant No.2021QNLM0200016)National Natural Science Foundation of China(42030103,41974119)Science Foundation from Innovation and Technology Support Program for Young Scientists in Colleges of Shandong province and Ministry of Science and Technology of China(2019RA2136)
文摘Unlike the real-valued plane wave reflection coefficient(PRC)at the pre-critical incident angles,the frequency-and depth-dependent spherical-wave reflection coefficient(SRC)is more accurate and always a complex value,which contains more reflection amplitude and phase information.In near field,the imaginary part of complex SRC(phase)cannot be ignored,but it is rarely considered in seismic inversion.To promote the practical application of spherical-wave seismic inversion,a novel spherical-wave inversion strategy is implemented.The complex-valued spherical-wave synthetic seismograms can be obtained by using a simple harmonic superposition model.It is assumed that geophone can only record the real part of complex-valued seismogram.The imaginary part can be further obtained by the Hilbert transform operator.We also propose the concept of complex spherical-wave elastic impedance(EI)and the complex spherical-wave EI equation.Finally,a novel complex spherical-wave EI inversion approach is proposed,which can fully use the reflection information of amplitude,phase,and frequency.With the inverted complex spherical-wave EI,the velocities and density can be further extracted.Synthetic data and field data examples show that the elastic parameters can be reasonably estimated,which illustrate the potential of our spherical-wave inversion approach in practical applications.
文摘The propagation characteristics of impact waves across a planar interface between a ceramic layer and a ceramic/metal(C/M) composite layer were investigated. Two interfacial boundary conditions were considered: one was a shear coupling boundary condition that simulated a perfectly bonded interface between the ceramic and composite, and the other was a slip boundary condition that only allowed a transmission of the transverse motion and normal stress at the interface. The ceramic was subjected to an incident impact wave. The ceramic and composite was assumed to be elastic during impact. The study was based on a basic method provided by Furlong, Westburg and Phillips for predicting the reflection and refraction of spherical waves across a planar interface separating two elastic solids. Emphasis was put on the effect of the metal volume fraction in the composite, ceramic thickness and interfacial boundary condition on the reflected waves. New and interesting results are obtained that provide a very useful guidance for design of a ceramic/composite armor and of a C/M functionally graded appliqué.
基金Supported by the PetroChina Science and Technology Project(2021DJ4002,2022DJ3908)。
文摘Acoustic reflection imaging logging technology can detect and evaluate the development of reflection anomalies,such as fractures,caves and faults,within a range of tens of meters from the wellbore,greatly expanding the application scope of well logging technology.This article reviews the development history of the technology and focuses on introducing key methods,software,and on-site applications of acoustic reflection imaging logging technology.Based on the analyses of major challenges faced by existing technologies,and in conjunction with the practical production requirements of oilfields,the further development directions of acoustic reflection imaging logging are proposed.Following the current approach that utilizes the reflection coefficients,derived from the computation of acoustic slowness and density,to perform seismic inversion constrained by well logging,the next frontier is to directly establish the forward and inverse relationships between the downhole measured reflection waves and the surface seismic reflection waves.It is essential to advance research in imaging of fractures within shale reservoirs,the assessment of hydraulic fracturing effectiveness,the study of geosteering while drilling,and the innovation in instruments of acoustic reflection imaging logging technology.
基金the sponsorship of the National 973 Program of China (2013CB228604)the National Grand Project for Science and Technology (2011ZX05030-004-002, 2011ZX05019-003 and 2011ZX05006-002) for funding this research+2 种基金the support of the Australian and Western Australian Governments and the North West Shelf Joint Venture Partnersthe Western Australian Energy Research Alliance (WA:ERA)Foundation from Geophysical Key Lab of SINOPEC (WTYJYWX2013-04-01)
文摘Linearized approximations of reflection and transmission coefficients set a foundation for amplitude versus offset（AVO） analysis and inversion in exploration geophysics.However,the weak properties contrast hypothesis of those linearized approximate equations leads to big errors when the two media across the interface vary dramatically.To extend the application of AVO analysis and inversion to high contrast between the properties of the two layers,we derive a novel nonlinearized high-contrast approximation of the PP-wave reflection coefficient,which establishes the direct relationship between PPwave reflection coefficient and P-wave velocities,S-wave velocities and densities across the interface.（A PP wave is a reflected compressional wave from an incident compressional wave（P-wave）.） This novel approximation is derived from the exact reflection coefficient equation with Taylor expansion for the incident angle.Model tests demonstrate that,compared with the reflection coefficients of the linearized approximations,the reflection coefficients of the novel nonlinearized approximate equation agree with those of the exact PP equation better for a high contrast interface with a moderate incident angle.Furthermore,we introduce a nonlinear direct inversion method utilizing the novel reflection coefficient equation as forward solver,to implement the direct inversion for the six parameters including P-wave velocities,S-wave velocities,and densities in the upper and lower layers across the interface.This nonlinear inversion algorithm is able to estimate the inverse of the nonlinear function in terms of model parameters directly rather than in a conventional optimization way.Three examples verified the feasibility and suitability of this novel approximation for a high contrast interface,and we still could estimate the six parameters across the interface reasonably when the parameters in both media across the interface vary about 50%.
基金supported by the National Natural Science Foundation of China (Grant No. 41688103)the Strategic Priority Research Program (A) of the Chinese Academy of Sciences (Grant No. XDA20070302)+1 种基金the Independent Project of the State Key Laboratory of the Lithospheric Evolution, IGGCAS (SKL-Z201704-11712180)The field work for seismic data collection was financially supported by the Projects (Grant Nos. SinoProbe-02-03, 2011ZX05008-001)
文摘A new method is developed to constrain S-wave velocity structures of the shallow crust based on frequencydependent amplitudes of direct P-waves in P-wave receiver functions(P-RFs). This method involves the following two steps:first, the high-frequency approximate amplitude formula of direct P-waves in P-RFs of individual stations is used to fit the observed amplitude distribution against the ray parameters at different frequencies, and second, the S-wave velocity depth profile beneath each station is constrained according to an empirical correlation between frequency and depth. Unlike traditional inversion techniques, the newly developed method is not dependent on initial velocity models, and the lateral and vertical resolutions of the results are controlled by the interstation distance and the data frequency, respectively. The effectiveness of the method is verified by synthetic tests on various models. The method is then applied to teleseismic P-RF data from a NW-SEtrending linear seismic array extending from the northeastern Tibetan Plateau to the central Sichuan Basin to construct an S-wave velocity image of the shallow crust along the array. The imaged velocity structure is further analysed and compared with the regional geology. In particular, the structural differences of sedimentary basins in the cratonic area of the stable Sichuan Basin and tectonically active belts in northeastern Tibet are investigated. By combining our results with previous observations, the relationship between the surficial geology and deep processes in the study region is also discussed.
基金financially supported by the National Key Research and Development Program of China (No.2021YFC2800902)the Basic Research Program of Qinghai Province (2023-ZJ-703)the National Natural Science Foundation of China (Nos.22178379,22127812)。
文摘Understanding the acoustic characteristics of hydrates in various sediments is crucial for hydrate resource detection and safe and efficient exploitation,as hydrate occurrence patterns vary greatly in different sediments.In this work,sediments with different bentonite contents,water saturations,and types were prepared to investigate the characteristics of P-wave velocity(reflecting the magnitude of hydrate saturation in the sediment)and amplitude(reflecting the degree of hydrate-sediment cementation)during hydrate formation and depressurization.During hydrate formation,the P-wave velocity and amplitude have similar trends.As clay content increases,the P-wave velocity increase rates quickened.On the other hand,the increased rate of P-wave velocity slows down with the increase of water saturation in the clay-bearing sediments.Comparing various types of sediment shows that the water absorption and swelling of bentonite reduce the pore space,speeding up the cementation of the hydrate with the sediment and increasing P-wave velocity at a faster rate.Correspondence between P-wave velocity and hydrate saturation is strongly related to sediment type,clay content,and water saturation.The rapidly decreasing amplitude in the early stage of hydrate depressurization indicates that hydrate in clay-bearing sediments is weakly cemented to the sediments,which is prone to stratigraphic instability.The findings of this study offer guidance for hydrate resource assessments in clay-bearing sediments as well as geologic risk estimations during hydrate mining.
基金supported by the National Key R&D Program of China(No.2018YFE0197600)European Union’s Horizon 2020 Research and Innovation Programme RISE under Grant Agreement No.823759(REMESH)the National Natural Science Foundation of China(No.52071244).
文摘The water-lubricated thrust bearings of the marine rim-driven thruster(RDT)are usually composed of polymer composites,which are prone to serious wear under harsh working conditions.Ultrasonic is an excellent non-destructive monitoring technology,but polymer materials are characterized by viscoelasticity,heterogeneity,and large acoustic attenuation,making it challenging to extract ultrasonic echo signals.Therefore,this paper proposes a wear monitoring method based on the amplitude spectrum of the ultrasonic reflection coefficient.The effects of bearing parameters,objective function,and algorithm parameters on the identification results are simulated and analyzed.Taking the correlation coefficient and root mean square error as the matching parameters,the thickness,sound velocity,density,and attenuation factor of the bearing are inversed simultaneously by utilizing the differential evolution algorithm(DEA),and the wear measurement system is constructed.In order to verify the identification accuracy of this method,an accelerated wear test under heavy load was executed on a multi-functional vertical water lubrication test rig with poly-ether-etherketone(PEEK)fixed pad and stainless-steel thrust collar as the object.The thickness of pad was measured using the high-precision spiral micrometer and ultrasonic testing system,respectively.Ultimately,the results demonstrate that the thickness identification error of this method is approximately 1%,and in-situ monitoring ability will be realized in the future,which is of great significance to the life prediction of bearings.
