Converted waves have slow velocity and low signal-to-noise ratio. It is also difficult to pick first-breaks and bin the common-conversion-points （CCP）. Some statics methods, which work well for P-wave data, can＇t b...Converted waves have slow velocity and low signal-to-noise ratio. It is also difficult to pick first-breaks and bin the common-conversion-points （CCP）. Some statics methods, which work well for P-wave data, can＇t be effectively used for solving convertedwave statics problems. This has become the main obstacle to breakthroughs in convertedwave data processing. To improve converted-wave static corrections, first, a statics method based on the common-receiver-point （CRP） stack is used for the initial receiver static correction to enhance the coherency of the CRP stack. Second, a stack-power-maximization static correction which improves the continuity of the CCP stack is used for detailed receiver statics. Finally, a non-surface-consistent residual moveout correction of the CCP gathers is used to enhance the stack power of reflection signals from different depths. Converted-wave statics are solved by the joint use of the three correction methods.展开更多
Pseudo-offset migration （POM） is a new method for prestack time migration of converted waves that improves on equivalent-offset migration （EOM）. The mapping of POM is different than EOM but the purpose of the two ...Pseudo-offset migration （POM） is a new method for prestack time migration of converted waves that improves on equivalent-offset migration （EOM）. The mapping of POM is different than EOM but the purpose of the two methods is to map the input samples to the common conversion scatter point （CCSP） gathers. This paper introduces the principles of the two migration methods and model parameter sensitivity tests for both POM and EOM. At large offset-to-depth ratios the hyperbolic approximation, the three-term approximation and the double square root （DSR） equation are used to NMO-correct the mapped POM gathers to obtain more accurate migration velocities. These equations were derived and calculated by small pseudo offset. POM is then used to image complex structure and prestack time migration.展开更多
The conventional fast converted-wave imaging method directly uses backward Pand converted S-wavefield to produce joint images. However, this image is accompanied by strong background noises, because the wavefi elds in...The conventional fast converted-wave imaging method directly uses backward Pand converted S-wavefield to produce joint images. However, this image is accompanied by strong background noises, because the wavefi elds in all propagation directions contribute to it. Given this issue, we improve the conventional imaging method in the two aspects. First, the amplitude-preserved P-and S-wavef ield are obtained by using an improved space-domain wavef ield separation scheme to decouple the original elastic wavef ield. Second, a convertedwave imaging condition is constructed based on the directional-wavefield separation and only the wavefields propagating in the same directions used for cross-correlation imaging, resulting in effectively eliminating the imaging artifacts of the wavefields with different directions;Complex-wavefi eld extrapolation is adopted to decompose the decoupled P-and S-wavefield into directional-wavefields during backward propagation, this improves the eff iciency of the directional-wavef ield separation. Experiments on synthetic data show that the improved method generates more accurate converted-wave images than the conventional one. Moreover, the improved method has application potential in micro-seismic and passive-source exploration due to its source-independent characteristic.展开更多
Several parameters are needed to describe the converted-wave （C-wave） moveout in processing multi-component seismic data, because of asymmetric raypaths and anisotropy. As the number of parameters increases, the con...Several parameters are needed to describe the converted-wave （C-wave） moveout in processing multi-component seismic data, because of asymmetric raypaths and anisotropy. As the number of parameters increases, the converted wave data processing and analysis becomes more complex. This paper develops a new moveout equation with two parameters for C-waves in vertical transverse isotropy （VTI） media. The two parameters are the C-wave stacking velocity （Vc2） and the squared velocity ratio （7v,i） between the horizontal P-wave velocity and C-wave stacking velocity. The new equation has fewer parameters, but retains the same applicability as previous ones. The applicability of the new equation and the accuracy of the parameter estimation are checked using model and real data. The form of the new equation is the same as that for layered isotropic media. The new equation can simplify the procedure for C-wave processing and parameter estimation in VTI media, and can be applied to real C-wave processing and interpretation. Accurate Vc2 and Yvti can be deduced from C-wave data alone using the double-scanning method, and the velocity ratio model is suitable for event matching between P- and C-wave data.展开更多
Ocean-Bottom Node(OBN)acquisitions provide both non-converted and converted reflection energy.There is a clear advantage to independently imaging both P-and S-waves,as they provide more information collectively than e...Ocean-Bottom Node(OBN)acquisitions provide both non-converted and converted reflection energy.There is a clear advantage to independently imaging both P-and S-waves,as they provide more information collectively than either does alone.In many conventional converted-wave pre-stack migration algorithms,density is treated as a constant,which is not the real-life case on earth.S-wave velocity and density information is crucial for hydrocarbon detection because it helps in the identification of porefilling fluids.In this paper,we focused on the effect of density on imaging,and developed a method of reverse-time migration(RTM)on converted s-waves of varying densities(VD-RTMCS).Phase correction was required prior to pre-stack migration to avoid constructive interference between data from adjacent sources.Synthetic data examples showed that when density variations were included,image profiles showed advantages in signal-to-noise ratio,vertical resolution and imaging of complex structures.展开更多
文摘Converted waves have slow velocity and low signal-to-noise ratio. It is also difficult to pick first-breaks and bin the common-conversion-points （CCP）. Some statics methods, which work well for P-wave data, can＇t be effectively used for solving convertedwave statics problems. This has become the main obstacle to breakthroughs in convertedwave data processing. To improve converted-wave static corrections, first, a statics method based on the common-receiver-point （CRP） stack is used for the initial receiver static correction to enhance the coherency of the CRP stack. Second, a stack-power-maximization static correction which improves the continuity of the CCP stack is used for detailed receiver statics. Finally, a non-surface-consistent residual moveout correction of the CCP gathers is used to enhance the stack power of reflection signals from different depths. Converted-wave statics are solved by the joint use of the three correction methods.
基金This work is sponsored by the Nation's Key Scientific & Technologic Projects (2003 BA613-09).
文摘Pseudo-offset migration （POM） is a new method for prestack time migration of converted waves that improves on equivalent-offset migration （EOM）. The mapping of POM is different than EOM but the purpose of the two methods is to map the input samples to the common conversion scatter point （CCSP） gathers. This paper introduces the principles of the two migration methods and model parameter sensitivity tests for both POM and EOM. At large offset-to-depth ratios the hyperbolic approximation, the three-term approximation and the double square root （DSR） equation are used to NMO-correct the mapped POM gathers to obtain more accurate migration velocities. These equations were derived and calculated by small pseudo offset. POM is then used to image complex structure and prestack time migration.
基金supported by the National Science and Technology Major Project of China(No.2017ZX05018-005)National Natural Science Foundation of China(No.41474110)
文摘The conventional fast converted-wave imaging method directly uses backward Pand converted S-wavefield to produce joint images. However, this image is accompanied by strong background noises, because the wavefi elds in all propagation directions contribute to it. Given this issue, we improve the conventional imaging method in the two aspects. First, the amplitude-preserved P-and S-wavef ield are obtained by using an improved space-domain wavef ield separation scheme to decouple the original elastic wavef ield. Second, a convertedwave imaging condition is constructed based on the directional-wavefield separation and only the wavefields propagating in the same directions used for cross-correlation imaging, resulting in effectively eliminating the imaging artifacts of the wavefields with different directions;Complex-wavefi eld extrapolation is adopted to decompose the decoupled P-and S-wavefield into directional-wavefields during backward propagation, this improves the eff iciency of the directional-wavef ield separation. Experiments on synthetic data show that the improved method generates more accurate converted-wave images than the conventional one. Moreover, the improved method has application potential in micro-seismic and passive-source exploration due to its source-independent characteristic.
基金sponsored by the National Natural Science Foundation of China(No.41074080)the National Science and Technology Major Project(No.2011ZX05019-008)+1 种基金the Science Foundation of China University of Petroleum-Beijing(No.KYJJ2012-05-11)the PetroChina Innovation Foundation(No.2012D-5006-0301)
文摘Several parameters are needed to describe the converted-wave （C-wave） moveout in processing multi-component seismic data, because of asymmetric raypaths and anisotropy. As the number of parameters increases, the converted wave data processing and analysis becomes more complex. This paper develops a new moveout equation with two parameters for C-waves in vertical transverse isotropy （VTI） media. The two parameters are the C-wave stacking velocity （Vc2） and the squared velocity ratio （7v,i） between the horizontal P-wave velocity and C-wave stacking velocity. The new equation has fewer parameters, but retains the same applicability as previous ones. The applicability of the new equation and the accuracy of the parameter estimation are checked using model and real data. The form of the new equation is the same as that for layered isotropic media. The new equation can simplify the procedure for C-wave processing and parameter estimation in VTI media, and can be applied to real C-wave processing and interpretation. Accurate Vc2 and Yvti can be deduced from C-wave data alone using the double-scanning method, and the velocity ratio model is suitable for event matching between P- and C-wave data.
基金supported by the National Science and Technology Major Project (No. 2016ZX05027-002)the National Natural Science Foundation of China (No. 41230 318)Qingdao National Laboratory for Marine Science and Technology Innovation Project of Ao-Shan (No. 2015ASKJ03)
文摘Ocean-Bottom Node(OBN)acquisitions provide both non-converted and converted reflection energy.There is a clear advantage to independently imaging both P-and S-waves,as they provide more information collectively than either does alone.In many conventional converted-wave pre-stack migration algorithms,density is treated as a constant,which is not the real-life case on earth.S-wave velocity and density information is crucial for hydrocarbon detection because it helps in the identification of porefilling fluids.In this paper,we focused on the effect of density on imaging,and developed a method of reverse-time migration(RTM)on converted s-waves of varying densities(VD-RTMCS).Phase correction was required prior to pre-stack migration to avoid constructive interference between data from adjacent sources.Synthetic data examples showed that when density variations were included,image profiles showed advantages in signal-to-noise ratio,vertical resolution and imaging of complex structures.
