Fluid and effective fracture identification in reservoirs is a crucial part of reservoir prediction.The frequency-dependent AVO inversion algorithms have proven to be effective for identifying fluid through its disper...Fluid and effective fracture identification in reservoirs is a crucial part of reservoir prediction.The frequency-dependent AVO inversion algorithms have proven to be effective for identifying fluid through its dispersion property.However,the conventional frequency-dependent AVO inversion algorithms based on Smith&Gidlow and Aki&Richards approximations do not consider the acquisition azimuth of seismic data and neglect the effect of seismic anisotropic dispersion in the actual medium.The aligned fractures in the subsurface medium induce anisotropy.The seismic anisotropy should be considered while accounting for the seismic dispersion properties through fluid-saturated fractured reservoirs.Anisotropy in such reservoirs is frequency-related due to wave-induced fluid-flow(WIFF)between interconnected fractures and pores.It can be used to identify fluid and effective fractures(fluid-saturated)by using azimuthal seismic data via anisotropic dispersion properties.In this paper,based on Rüger’s equation,we derived an analytical expression in the frequency domain for the frequencydependent AVOAz inversion in terms of fracture orientation,dispersion gradient of isotropic background rock,anisotropic dispersion gradient,and the dispersion at a normal incident angle.The frequency-dependent AVOAz equation utilizes azimuthal seismic data and considers the effect of both isotropic and anisotropic dispersion.Reassigned Gabor Transform(RGT)is used to achieve highresolution frequency division data.We then propose the frequency-dependent AVOAz inversion method to identify fluid and characterize effective fractures in fractured porous reservoirs.Through application to high-qualified seismic data of dolomite and carbonate reservoirs,the results show that the method is useful for identifying fluid and effective fractures in fluid-saturated fractured rocks.展开更多
Dynamic stability analyses of structures are becoming increasing prevalent in applications for tall buildings and space structure designs. This paper presents an effective energy criterion for identifying the dynamic ...Dynamic stability analyses of structures are becoming increasing prevalent in applications for tall buildings and space structure designs. This paper presents an effective energy criterion for identifying the dynamic stability of generalized structures through the modification of an earlier developed energy criterion for hardening structures. Two time-varying effective energy indices are introduced to account for the dynamic stability of both the hardening and deteriorating structures; one for the description of structural properties, i.e., the structural effective intrinsic energy, and the other for the measurement of the input energy, i.e., the valid external work. It is shown that a structure's stability can survive provided the effective intrinsic energy is always less than the valid external work during a dynamic excitation. The first passage of the effective intrinsic energy over the valid external work indicates the dynamic instability of the structure. A comparison study is carried out regarding the validity and applicability between the energy and effective energy criteria as applied to the dynamic stability analysis of three different structures.展开更多
基金supported by the National Major Science and Technology Project of China(2016ZX05004003)the National Natural Science Foundation of China(41574103,41974120,U20B2015)Open Fund of State Key Laboratory of Coal Resources and Safe Mining(Grant No.SKLCRSM19KFA08)。
文摘Fluid and effective fracture identification in reservoirs is a crucial part of reservoir prediction.The frequency-dependent AVO inversion algorithms have proven to be effective for identifying fluid through its dispersion property.However,the conventional frequency-dependent AVO inversion algorithms based on Smith&Gidlow and Aki&Richards approximations do not consider the acquisition azimuth of seismic data and neglect the effect of seismic anisotropic dispersion in the actual medium.The aligned fractures in the subsurface medium induce anisotropy.The seismic anisotropy should be considered while accounting for the seismic dispersion properties through fluid-saturated fractured reservoirs.Anisotropy in such reservoirs is frequency-related due to wave-induced fluid-flow(WIFF)between interconnected fractures and pores.It can be used to identify fluid and effective fractures(fluid-saturated)by using azimuthal seismic data via anisotropic dispersion properties.In this paper,based on Rüger’s equation,we derived an analytical expression in the frequency domain for the frequencydependent AVOAz inversion in terms of fracture orientation,dispersion gradient of isotropic background rock,anisotropic dispersion gradient,and the dispersion at a normal incident angle.The frequency-dependent AVOAz equation utilizes azimuthal seismic data and considers the effect of both isotropic and anisotropic dispersion.Reassigned Gabor Transform(RGT)is used to achieve highresolution frequency division data.We then propose the frequency-dependent AVOAz inversion method to identify fluid and characterize effective fractures in fractured porous reservoirs.Through application to high-qualified seismic data of dolomite and carbonate reservoirs,the results show that the method is useful for identifying fluid and effective fractures in fluid-saturated fractured rocks.
基金supported by the National Natural Science Foundation of China(Grant Nos.51261120374 and 51538010)
文摘Dynamic stability analyses of structures are becoming increasing prevalent in applications for tall buildings and space structure designs. This paper presents an effective energy criterion for identifying the dynamic stability of generalized structures through the modification of an earlier developed energy criterion for hardening structures. Two time-varying effective energy indices are introduced to account for the dynamic stability of both the hardening and deteriorating structures; one for the description of structural properties, i.e., the structural effective intrinsic energy, and the other for the measurement of the input energy, i.e., the valid external work. It is shown that a structure's stability can survive provided the effective intrinsic energy is always less than the valid external work during a dynamic excitation. The first passage of the effective intrinsic energy over the valid external work indicates the dynamic instability of the structure. A comparison study is carried out regarding the validity and applicability between the energy and effective energy criteria as applied to the dynamic stability analysis of three different structures.
