At present, near-surface shear wave velocities are mainly calculated through Rayleigh wave dispersion-curve inversions in engineering surface investigations, but the required calculations pose a highly nonlinear globa...At present, near-surface shear wave velocities are mainly calculated through Rayleigh wave dispersion-curve inversions in engineering surface investigations, but the required calculations pose a highly nonlinear global optimization problem. In order to alleviate the risk of falling into a local optimal solution, this paper introduces a new global optimization method, the shuffle frog-leaping algorithm （SFLA）, into the Rayleigh wave dispersion-curve inversion process. SFLA is a swarm-intelligence-based algorithm that simulates a group of frogs searching for food. It uses a few parameters, achieves rapid convergence, and is capability of effective global searching. In order to test the reliability and calculation performance of SFLA, noise-free and noisy synthetic datasets were inverted. We conducted a comparative analysis with other established algorithms using the noise-free dataset, and then tested the ability of SFLA to cope with data noise. Finally, we inverted a real-world example to examine the applicability of SFLA. Results from both synthetic and field data demonstrated the effectiveness of SFLA in the interpretation of Rayleigh wave dispersion curves. We found that SFLA is superior to the established methods in terms of both reliability and computational efficiency, so it offers great potential to improve our ability to solve geophysical inversion problems.展开更多
Most sedimentary formations with fine layers can be characterized as transversely isotropic media.The evaluation of shear-wave anisotropy is critical in logging-while-drilling(LWD)applications.We developed a joint met...Most sedimentary formations with fine layers can be characterized as transversely isotropic media.The evaluation of shear-wave anisotropy is critical in logging-while-drilling(LWD)applications.We developed a joint method to simultaneously invert formation shear-wave anisotropy and vertical shear velocity using LWD monopole and dipole dispersion data.Theoretical analysis demonstrates that formation shear-wave anisotropy significantly aff ects the dispersion characteristics of Stoneley and formation flexural waves.The inversion objective function was constructed based on the change in dispersion characteristics and was weighted by the spectra of multipole waves.Numerical results using synthetic examples demonstrate that the joint inversion method can not only alleviate the non-uniqueness problem but also help improve the accuracy of the inversion results.The comparison of diff erent signal-to-noise ratio inversion results proved that the weighted inversion method is more accurate and stable.展开更多
In petroleum seismic exploration,dense seismic ray coverage is often guaranteed through dense seismic sources and geophones.Dense ray coverage facilitates the high-resolution 3D velocity structure imaging of near surf...In petroleum seismic exploration,dense seismic ray coverage is often guaranteed through dense seismic sources and geophones.Dense ray coverage facilitates the high-resolution 3D velocity structure imaging of near surfaces using surface waves.In this study,the 3D velocity and anisotropy structure of a petroleum exploration area are obtained using the azimuth-dependent dispersion curve inversion(ADDCI)method.Imaging results show that low-velocity zones correspond to a river channel.The fast propagation direction(FPD)of S-waves along this channel is basically consistent with the direction of the channel.The eastern part of the study area has a surface sediment layer with a thickness of less than 20 m,which corresponds to the sand and gravel deposits formed by the river alluvial deposition near the surface.In addition,a relatively thick sedimentary layer is formed on the southern side of the study area.The anisotropy shows that the FPD is positively correlated with the direction of alluvial fl ow and that the magnitude of anisotropy in the deep part is greater than that in the shallow part.Inversion results are basically consistent with the geological data and suggest that the obtained model can truly refl ect the 3D velocity structure and anisotropy of the near-surface area.This study shows that the ADDCI method can maximize the high-energy surface waves in exploration data to obtain near-surface velocity structures,which provide a highly accurate model for near-surface static correction.展开更多
基金supported by the National Natural Science Foundation of China(No.41374123)
文摘At present, near-surface shear wave velocities are mainly calculated through Rayleigh wave dispersion-curve inversions in engineering surface investigations, but the required calculations pose a highly nonlinear global optimization problem. In order to alleviate the risk of falling into a local optimal solution, this paper introduces a new global optimization method, the shuffle frog-leaping algorithm （SFLA）, into the Rayleigh wave dispersion-curve inversion process. SFLA is a swarm-intelligence-based algorithm that simulates a group of frogs searching for food. It uses a few parameters, achieves rapid convergence, and is capability of effective global searching. In order to test the reliability and calculation performance of SFLA, noise-free and noisy synthetic datasets were inverted. We conducted a comparative analysis with other established algorithms using the noise-free dataset, and then tested the ability of SFLA to cope with data noise. Finally, we inverted a real-world example to examine the applicability of SFLA. Results from both synthetic and field data demonstrated the effectiveness of SFLA in the interpretation of Rayleigh wave dispersion curves. We found that SFLA is superior to the established methods in terms of both reliability and computational efficiency, so it offers great potential to improve our ability to solve geophysical inversion problems.
基金supported by the National Natural Science Foundation of China (Grant No.12174421)the Hubei Key Laboratory of Advanced Aerospace Propulsion Technology (Grant No.KFJJ2020-02).
文摘Most sedimentary formations with fine layers can be characterized as transversely isotropic media.The evaluation of shear-wave anisotropy is critical in logging-while-drilling(LWD)applications.We developed a joint method to simultaneously invert formation shear-wave anisotropy and vertical shear velocity using LWD monopole and dipole dispersion data.Theoretical analysis demonstrates that formation shear-wave anisotropy significantly aff ects the dispersion characteristics of Stoneley and formation flexural waves.The inversion objective function was constructed based on the change in dispersion characteristics and was weighted by the spectra of multipole waves.Numerical results using synthetic examples demonstrate that the joint inversion method can not only alleviate the non-uniqueness problem but also help improve the accuracy of the inversion results.The comparison of diff erent signal-to-noise ratio inversion results proved that the weighted inversion method is more accurate and stable.
基金supported by the National Key Research and Development Program of China(No.2017YFC0601206)the Science and Technology Innovation(Seedling Project)Cultivation Program of Sichuan Province in 2020(No.2020127)the National Natural Science Foundation of China(Nos.41674059,41340009)。
文摘In petroleum seismic exploration,dense seismic ray coverage is often guaranteed through dense seismic sources and geophones.Dense ray coverage facilitates the high-resolution 3D velocity structure imaging of near surfaces using surface waves.In this study,the 3D velocity and anisotropy structure of a petroleum exploration area are obtained using the azimuth-dependent dispersion curve inversion(ADDCI)method.Imaging results show that low-velocity zones correspond to a river channel.The fast propagation direction(FPD)of S-waves along this channel is basically consistent with the direction of the channel.The eastern part of the study area has a surface sediment layer with a thickness of less than 20 m,which corresponds to the sand and gravel deposits formed by the river alluvial deposition near the surface.In addition,a relatively thick sedimentary layer is formed on the southern side of the study area.The anisotropy shows that the FPD is positively correlated with the direction of alluvial fl ow and that the magnitude of anisotropy in the deep part is greater than that in the shallow part.Inversion results are basically consistent with the geological data and suggest that the obtained model can truly refl ect the 3D velocity structure and anisotropy of the near-surface area.This study shows that the ADDCI method can maximize the high-energy surface waves in exploration data to obtain near-surface velocity structures,which provide a highly accurate model for near-surface static correction.
