Seismic quantitative reservoir simulations and characterizations have played a vital role in exploring stratigraphic traps,such as lateaggradational lowstands prograding wedge systems(LPWS)within lowstands systems tra...Seismic quantitative reservoir simulations and characterizations have played a vital role in exploring stratigraphic traps,such as lateaggradational lowstands prograding wedge systems(LPWS)within lowstands systems tracts(LST).However,seismic data acquisition operations are always dominated by exceptional seismic coherent noise events,e.g.,multiples,which reduce the signal strengths of the sourcegenerated incident seismic waves within vertically and laterally heterogeneous earth systems.Hence,these noise events create hurdles in predicting paleo-depositional impedance(PDI),paleo-thickness(PTS),paleo-dense fractured networks,erosional and depositional zones,faultcontrolled migrations,and types of seismic reflection configurations(SRFC),which are key elements in developing stratigraphic pinch-out traps.This research utilizes the state-of-the-art technologies of spectral wavelet-based instantaneous time-frequency analysis and seismic waveform frequency-controlled porosity-constrained static reservoir simulation(FDPVS)tools to quantify the LPWS inside the Onshore Basin,Pakistan.The use of conventional amplitude-based seismic attributes,such as the average energy,remained a better tool for deciphering the overall geological architecture of the LPWS.Conventional FDPVS realizations resolved a PDI of−1.391 gm./c.c.^(*)m/s to−0.97 gm./c.c.^(*)m/s for LPWS with PTS of 12 and 20 m,respectively.A 0.9 km lateral extent of paleo-dense fractured networks(PDFN)with a strong linear regression R^(2)=0.93 was also resolved.Average energy attribute-based instantaneous frequency FDPVS realizations enabled the imaging of parallel-toprograding SRFC with resolved magnitudes of−0.259 gm./c.c.^(*)m/s for PDI,20 m for PTS,and 0.73 km for PDFN with linear regression transforms at R^(2)=0.92,which indicates the deposition of onlap fill facies inside the LPWS during extensive sea-level fall.These realizations have also resolved frequency-controlled fault migrations on 27-Hz spectral waveform-based amplitude plots with 2.174 gm./c.c.^(*)m/s PDI for conduit fault systems and 27-Hz with 0.585 gm./c.c.^(*)m/s PDI for sealing fault systems.All these structural configurations are completely sealed up by transgressive seals of transgressive systems tracts and,hence,developed into pure stratigraphic-based oil and gas plays.This research has strong implications for side-tracking drilling locations and provides an analogue for basins with similar geology and stratigraphy worldwide.展开更多
Southwest China is a tectonically and seismically active region,witnessing strong deformation due to the collision between the Indian and Eurasian plates.Constraining the subsurface velocity structure of this region i...Southwest China is a tectonically and seismically active region,witnessing strong deformation due to the collision between the Indian and Eurasian plates.Constraining the subsurface velocity structure of this region is thus important in understanding the tectonics and geodynamic processes of continental collision and in mitigating seismic hazards.Numerous studies have provided various 3D seismic velocity models in southwest China.However,discrepancies exist among these models,and less effort has been made to quantify the reliability and accuracy of these existing velocity models.In this study,we use regional 3D waveform simulation to evaluate the performance of various regional crustal 3D velocity models in reproducing observed seismograms.We particularly focus on two recent earthquake sequence in the region,the 2021 Yunnan Yangbi MS_(6.4)earthquake sequence and the 2022 Sichuan Luding MS_(6.8)earthquake sequence.The tested 3D velocity models include the Southwest China Community Velocity model V1.0,the Unified Seismic Tomography Models for Continental China Lithosphere V2.0,the adjoint full waveform tomography model of the crustal and upper mantle beneath Eastern Tibetan Plateau,and the shallow seismic structure model beneath continental China.Our results show that the tested 3D velocity models generally capture well long-period(<0.2 Hz)waveforms,indicating that the 3D models adequately resolve overall large-scale subsurface structures.However,the 3D synthetics show discrepancies in higher frequencies(0.05–0.3 Hz)and the performance of the 3D velocity models varies from region to region,suggesting that smaller scale heterogeneities are not well constrained.Including shallow velocity structures(<10 km)can improve the waveform fitting,emphasizing the importance of incorporating shallow structures in waveform modeling.The full-waveform tomography model shows a slighter better performance than the other models,especially for the body-waves,highlighting the advantages of full-waveform method in achieving sub-wavelength resolution despite the usage of very long-period waveforms.In light of these comparison results of model performance,we identify the advantages and limitations of different seismic tomography models and methods,and we propose to incorporate different tomography methods and datasets to better constrain subsurface structures.While our target region in this study is southwest China,the analysis that we have conducted can be applied to other regions of various scales and tectonic settings for quantitative seismic model evaluation.展开更多
Tree height composition describes the relative abundance of trees in different height levels and performs as a critical characteristic for community ecology.The recent launched full-waveform spaceborne LiDAR(Light Det...Tree height composition describes the relative abundance of trees in different height levels and performs as a critical characteristic for community ecology.The recent launched full-waveform spaceborne LiDAR(Light Detection and Ranging),i.e.,Global Ecosystem Dynamics Investigation(GEDI),can map canopy height,but whether this observation reflects tree height composition remains untested.In this study,we firstly conduct numerical simulations to explore to what extent tree height composition can be obtained from GEDI waveform signals.We simulate waveforms for diverse forest scenarios using GEDI simulator coupled with LESS(LargE-Scale remote sensing data and image Simulation),a state-of-the-art radiative transfer model.We devise a minimalistic model,Tree generation based on Asymmetric generalized Gaussian(TAG),for customizing tree objects to accelerate forest scene creation.The results demonstrate that tree objects generated by TAG perform similarly in LiDAR simulation with objects from commercial 3-dimensional software.Results of simulated GEDI waveforms reasonably respond to the variation of crown architectures in even-aged forests.GEDI waveforms have an acceptable ability to identify different height layers within multi-layer forests,except for fir forests with a cone-shaped crown.The shape metric of waveforms reflects the height of each layer,while retrieval accuracy decreases with the increases in height variations within each layer.A 5-m interval between layers is the minimum requirement so that the different height layers can be separated.A mixture of different tree species reduces the retrieval accuracy of tree height layers.We also utilize real GEDI observations to retrieve tree heights in multi-height-layer forests.The findings indicate that GEDI waveforms are also efficient in identifying tree height composition in practical forest scenarios.Overall,results from this study demonstrate that GEDI waveforms can reflect the height composition within typical forest stands.展开更多
A topographic parameter inversion method based on laser altimetry is developed in this paper, which can be used to deduce the surface vertical profile and retrieve the topographic parameters within the laser footprint...A topographic parameter inversion method based on laser altimetry is developed in this paper, which can be used to deduce the surface vertical profile and retrieve the topographic parameters within the laser footprints by analyzing and simulating return waveforms. This method comprises three steps. The first step is to build the numerical models for the whole measuring procedure of laser altimetry, construct digital elevation models for surfaces with different topographic parameters, and calculate return waveforms. The second step is to analyze the simulated return waveforms to obtain their characteristics parameters, summarize the effects of the topographic parameter variations on the characteristic parameters of simulated return waveforms, and analyze the observed return waveforms of laser altimeters to acquire their characteristic parameters at the same time. The last step is to match the characteristic parameters of the simulated and observed return waveforms, and deduce the topographic parameters within the laser footprint. This method can be used to retrieve the topographic parameters within the laser footprint from the observed return waveforms of spaceborne laser altimeters and to get knowledge about the surface altitude distribution within the laser footprint other than only getting the height of the surface encountered firstly by the laser beam, which extends laser altimeters' function and makes them more like radars.展开更多
文摘Seismic quantitative reservoir simulations and characterizations have played a vital role in exploring stratigraphic traps,such as lateaggradational lowstands prograding wedge systems(LPWS)within lowstands systems tracts(LST).However,seismic data acquisition operations are always dominated by exceptional seismic coherent noise events,e.g.,multiples,which reduce the signal strengths of the sourcegenerated incident seismic waves within vertically and laterally heterogeneous earth systems.Hence,these noise events create hurdles in predicting paleo-depositional impedance(PDI),paleo-thickness(PTS),paleo-dense fractured networks,erosional and depositional zones,faultcontrolled migrations,and types of seismic reflection configurations(SRFC),which are key elements in developing stratigraphic pinch-out traps.This research utilizes the state-of-the-art technologies of spectral wavelet-based instantaneous time-frequency analysis and seismic waveform frequency-controlled porosity-constrained static reservoir simulation(FDPVS)tools to quantify the LPWS inside the Onshore Basin,Pakistan.The use of conventional amplitude-based seismic attributes,such as the average energy,remained a better tool for deciphering the overall geological architecture of the LPWS.Conventional FDPVS realizations resolved a PDI of−1.391 gm./c.c.^(*)m/s to−0.97 gm./c.c.^(*)m/s for LPWS with PTS of 12 and 20 m,respectively.A 0.9 km lateral extent of paleo-dense fractured networks(PDFN)with a strong linear regression R^(2)=0.93 was also resolved.Average energy attribute-based instantaneous frequency FDPVS realizations enabled the imaging of parallel-toprograding SRFC with resolved magnitudes of−0.259 gm./c.c.^(*)m/s for PDI,20 m for PTS,and 0.73 km for PDFN with linear regression transforms at R^(2)=0.92,which indicates the deposition of onlap fill facies inside the LPWS during extensive sea-level fall.These realizations have also resolved frequency-controlled fault migrations on 27-Hz spectral waveform-based amplitude plots with 2.174 gm./c.c.^(*)m/s PDI for conduit fault systems and 27-Hz with 0.585 gm./c.c.^(*)m/s PDI for sealing fault systems.All these structural configurations are completely sealed up by transgressive seals of transgressive systems tracts and,hence,developed into pure stratigraphic-based oil and gas plays.This research has strong implications for side-tracking drilling locations and provides an analogue for basins with similar geology and stratigraphy worldwide.
基金supported by the National Key R&D Program of China(Grant No.2022YFF0802600)the National Natural Science Foundation of China(Grant Nos.91958209 and 42288201)the Key Research Program of the Institute of Geology and Geophysics,Chinese Academy of Sciences(Grant No.IGGCAS-201904)。
文摘Southwest China is a tectonically and seismically active region,witnessing strong deformation due to the collision between the Indian and Eurasian plates.Constraining the subsurface velocity structure of this region is thus important in understanding the tectonics and geodynamic processes of continental collision and in mitigating seismic hazards.Numerous studies have provided various 3D seismic velocity models in southwest China.However,discrepancies exist among these models,and less effort has been made to quantify the reliability and accuracy of these existing velocity models.In this study,we use regional 3D waveform simulation to evaluate the performance of various regional crustal 3D velocity models in reproducing observed seismograms.We particularly focus on two recent earthquake sequence in the region,the 2021 Yunnan Yangbi MS_(6.4)earthquake sequence and the 2022 Sichuan Luding MS_(6.8)earthquake sequence.The tested 3D velocity models include the Southwest China Community Velocity model V1.0,the Unified Seismic Tomography Models for Continental China Lithosphere V2.0,the adjoint full waveform tomography model of the crustal and upper mantle beneath Eastern Tibetan Plateau,and the shallow seismic structure model beneath continental China.Our results show that the tested 3D velocity models generally capture well long-period(<0.2 Hz)waveforms,indicating that the 3D models adequately resolve overall large-scale subsurface structures.However,the 3D synthetics show discrepancies in higher frequencies(0.05–0.3 Hz)and the performance of the 3D velocity models varies from region to region,suggesting that smaller scale heterogeneities are not well constrained.Including shallow velocity structures(<10 km)can improve the waveform fitting,emphasizing the importance of incorporating shallow structures in waveform modeling.The full-waveform tomography model shows a slighter better performance than the other models,especially for the body-waves,highlighting the advantages of full-waveform method in achieving sub-wavelength resolution despite the usage of very long-period waveforms.In light of these comparison results of model performance,we identify the advantages and limitations of different seismic tomography models and methods,and we propose to incorporate different tomography methods and datasets to better constrain subsurface structures.While our target region in this study is southwest China,the analysis that we have conducted can be applied to other regions of various scales and tectonic settings for quantitative seismic model evaluation.
基金supported by the National Science Foun-dation of China(42141005)supported by the High-performance Computing Platform of Peking University.
文摘Tree height composition describes the relative abundance of trees in different height levels and performs as a critical characteristic for community ecology.The recent launched full-waveform spaceborne LiDAR(Light Detection and Ranging),i.e.,Global Ecosystem Dynamics Investigation(GEDI),can map canopy height,but whether this observation reflects tree height composition remains untested.In this study,we firstly conduct numerical simulations to explore to what extent tree height composition can be obtained from GEDI waveform signals.We simulate waveforms for diverse forest scenarios using GEDI simulator coupled with LESS(LargE-Scale remote sensing data and image Simulation),a state-of-the-art radiative transfer model.We devise a minimalistic model,Tree generation based on Asymmetric generalized Gaussian(TAG),for customizing tree objects to accelerate forest scene creation.The results demonstrate that tree objects generated by TAG perform similarly in LiDAR simulation with objects from commercial 3-dimensional software.Results of simulated GEDI waveforms reasonably respond to the variation of crown architectures in even-aged forests.GEDI waveforms have an acceptable ability to identify different height layers within multi-layer forests,except for fir forests with a cone-shaped crown.The shape metric of waveforms reflects the height of each layer,while retrieval accuracy decreases with the increases in height variations within each layer.A 5-m interval between layers is the minimum requirement so that the different height layers can be separated.A mixture of different tree species reduces the retrieval accuracy of tree height layers.We also utilize real GEDI observations to retrieve tree heights in multi-height-layer forests.The findings indicate that GEDI waveforms are also efficient in identifying tree height composition in practical forest scenarios.Overall,results from this study demonstrate that GEDI waveforms can reflect the height composition within typical forest stands.
基金supported by the National Hi-Tech Research and Development Program of China (Grant No. 2007AA12Z177)
文摘A topographic parameter inversion method based on laser altimetry is developed in this paper, which can be used to deduce the surface vertical profile and retrieve the topographic parameters within the laser footprints by analyzing and simulating return waveforms. This method comprises three steps. The first step is to build the numerical models for the whole measuring procedure of laser altimetry, construct digital elevation models for surfaces with different topographic parameters, and calculate return waveforms. The second step is to analyze the simulated return waveforms to obtain their characteristics parameters, summarize the effects of the topographic parameter variations on the characteristic parameters of simulated return waveforms, and analyze the observed return waveforms of laser altimeters to acquire their characteristic parameters at the same time. The last step is to match the characteristic parameters of the simulated and observed return waveforms, and deduce the topographic parameters within the laser footprint. This method can be used to retrieve the topographic parameters within the laser footprint from the observed return waveforms of spaceborne laser altimeters and to get knowledge about the surface altitude distribution within the laser footprint other than only getting the height of the surface encountered firstly by the laser beam, which extends laser altimeters' function and makes them more like radars.
