Passive surface wave imaging has been a powerful tool for near-surface characterization in urban areas,which extracts surface wave signals from ambient seismic noise and then estimates subsurface shear wave velocity b...Passive surface wave imaging has been a powerful tool for near-surface characterization in urban areas,which extracts surface wave signals from ambient seismic noise and then estimates subsurface shear wave velocity by inversion of the measured phase velocity.The high-frequency(approximately>1 Hz)seismic noise fields in urban environments are dominantly induced by human activities such as the vehicle traffic.Traffic seismic sources are nonrandomly distributed in time and space.Applying standard interferometric techniques to recordings from these nonrandom noise sources makes the Green’s function liable to estimation errors.We analyze the influence of using nonrandom traffic seismic sources for surface wave imaging.With nonrandom traffic seismic sources in time,spurious signals are generated in the cross-correlation function.With nonrandom traffic seismic sources in space,surface-wave phase velocities could be overestimated in the dispersion measurement.We provide an overview of solutions for surface-wave imaging with nonrandom traffic seismic sources in time and space,aiming to improve the retrieval of high-frequency surface waves and achieve reliable results from ultrashort(tens of seconds)observations for near-surface characterization.展开更多
The conventional method of seismic data acquisition geometry design is based on the assumption of horizontal subsurface reflectors, which often is not suitable for complex structure. We start from a controlled illumin...The conventional method of seismic data acquisition geometry design is based on the assumption of horizontal subsurface reflectors, which often is not suitable for complex structure. We start from a controlled illumination analysis and put forward a method of seismic survey geometry design for target-oriented imaging. The method needs a velocity model obtained by a preliminary seismic interpretation. The one-way Fourier finite-difference wave propagator is used to extrapolate plane wave sources on the target layer to the surface. By analyzing the wave energy distribution at the surface extrapolated from the target layer, the shot or receiver locations needed for target layer imaging can be determined. Numerical tests using the SEG-EAGE salt model suggest that this method is useful for confirming the special seismic acquisition geometry layout for target-oriented imaging.展开更多
Knowledge of the locations of seismic sources is critical for microseismic monitoring. Time-window-based elastic wave interferometric imaging and weighted- elastic-wave （WEW） interferometric imaging are proposed and...Knowledge of the locations of seismic sources is critical for microseismic monitoring. Time-window-based elastic wave interferometric imaging and weighted- elastic-wave （WEW） interferometric imaging are proposed and used to locate modeled microseismic sources. The proposed method improves the precision and eliminates artifacts in location profiles. Numerical experiments based on a horizontally layered isotropic medium have shown that the method offers the following advantages： It can deal with Iow-SNR microseismic data with velocity perturbations as well as relatively sparse receivers and still maintain relatively high precision despite the errors in the velocity model. Furthermore, it is more efficient than conventional traveltime inversion methods because interferometric imaging does not require traveltime picking. Numerical results using a 2D fault model have also suggested that the weighted-elastic-wave interferometric imaging can locate multiple sources with higher location precision than the time-reverse imaging method.展开更多
One of the problems experienced in marine geophysical exploration is that the layered features in the migration imaging profile are blurred and the seismic energy reflected is weaker in the middle or lower parts. In t...One of the problems experienced in marine geophysical exploration is that the layered features in the migration imaging profile are blurred and the seismic energy reflected is weaker in the middle or lower parts. In this study we model the seismic wavefield records in the undulating seafloor when there is both a slight change and significant change in seafloor topography to analyze its influence on the seismic reflection data and migration imaging profiles. We compare and analyze the wave field records collected at the same point on the original and modified velocity models, and the cross-bonding resulting migration imaging profiles. The results show that whether the seismic reflection data collection is performed along the direction of the survey line or against the direction of the survey line, slight changes in the seafloor topography have little effect on the wave field records and the migration profile, while significant changes in the seafloor topography have great effect on both the wave field records and migration profile.展开更多
Acquisition footprint is a new concept to describe the seismic noise in three-dimensional seismic exploration and it is closely related to geometry and observation shuttering.At present,the study on acquisition footpr...Acquisition footprint is a new concept to describe the seismic noise in three-dimensional seismic exploration and it is closely related to geometry and observation shuttering.At present,the study on acquisition footprints has become a hot spot.In partnership with the Dagang Oilfield,we used the channel sand body seismic physical model to study the characteristics of wide/narrow azimuth acquisition footprints and analyzed and compared the two types of footprints and their effects on target imaging.In addition,the footprints caused by data processing of the normal moveout offset(NMO)stretching aberration were discussed.These footprints are located only in the shallow or middle layer in the time slice,and possibly affect the imaging of shallow target layers,and have no influence on deep target imaging.Seismic physical modeling has its advantages in the study of acquisition footprints.展开更多
To solve problems in small-scale and complex structural traps,the inverse Gaussian-beam stack-imaging method is commonly used to process crosswell seismic wave reflection data.Owing to limited coverage,the imaging qua...To solve problems in small-scale and complex structural traps,the inverse Gaussian-beam stack-imaging method is commonly used to process crosswell seismic wave reflection data.Owing to limited coverage,the imaging quality of conventional ray-based crosswell seismic stack imaging is poor in complex areas;moreover,the imaging range is small and with sever interference because of the arc phenomenon in seismic migration.Thus,we propose the inverse Gaussian-beam stack imaging,in which Gaussian weight functions of rays contributing to the geophones energy are calculated and used to decompose the seismic wavefield.This effectively enlarges the coverage of the reflection points and improves the transverse resolution.Compared with the traditional VSP–CDP stack imaging,the proposed methods extends the imaging range,yields higher horizontal resolution,and is more adaptable to complex geological structures.The method is applied to model a complex structure in the K-area.The results suggest that the wave group of the target layer is clearer,the resolution is higher,and the main frequency of the crosswell seismic section is higher than that in surface seismic exploration The effectiveness and robustness of the method are verified by theoretical model and practical data.展开更多
Active source seismic method is generally used to image subsurface structures for resource exploration,including oil,gas and coal.Although it can provide highresolution subsurface structures,due to some economic and e...Active source seismic method is generally used to image subsurface structures for resource exploration,including oil,gas and coal.Although it can provide highresolution subsurface structures,due to some economic and environmental restrictions,it is not suitable in some cases.In recent 20 years,passive seismic survey based on ambient noise seismic interferometry(ANSI)has started to be widely used in imaging subsurface structures.In comparison,ANSI does not need active sources and can image subsurface structures at different depths as a lowcost alternative to active seismic exploration.展开更多
As dense seismic arrays at different scales are deployed,the techniques to make full use of array data with low computing cost become increasingly needed.The wave gradiometry method(WGM)is a new branch in seismic tomo...As dense seismic arrays at different scales are deployed,the techniques to make full use of array data with low computing cost become increasingly needed.The wave gradiometry method(WGM)is a new branch in seismic tomography,which utilizes the spatial gradients of the wavefield to determine the phase velocity,wave propagation direction,geometrical spreading,and radiation pattern.Seismic wave propagation parameters obtained using the WGM can be further applied to invert 3D velocity models,Q values,and anisotropy at lithospheric(crust and/or mantle)and smaller scales(e.g.,industrial oilfield or fault zone).Herein,we review the theoretical foundation,technical development,and major applications of the WGM,and compared the WGM with other commonly used major array imaging methods.Future development of the WGM is also discussed.展开更多
Shenhu area in South China Sea includes extensive collapse and diapir structures,forming high-angle faults and vertical fracture system,which functions as a fluid migration channel for gas hydrate formation.In order t...Shenhu area in South China Sea includes extensive collapse and diapir structures,forming high-angle faults and vertical fracture system,which functions as a fluid migration channel for gas hydrate formation.In order to improve the imaging precision of natural gas hydrate in this area,especially for fault and fracture structures,the present work propose a velocity stitching technique that accelerates effectively the convergence of the shallow seafloor,indicating seafloor horizon interpretation and the initial interval velocity for model building.In the depth domain,pre-stack depth migration and residual curvature are built into the model based on high-precision grid-tomography velocity inversion,after several rounds of tomographic iterations,as the residual velocity field converges gradually.Test results of the Shenhu area show that the imaging precision of the fault zone is obviously improved,the fracture structures appear more clearly,the wave group characteristics significantly change for the better and the signal-to-noise ratio and resolution are improved.These improvements provide the necessary basis for the new reservoir model and field drilling risk tips,help optimize the favorable drilling target,and are crucial for the natural gas resource potential evaluation.展开更多
In common practice in the oil fields,the injection of water and gas into reservoirs is a crucial technique to increase production.The control of the waterflooding front in oil/gas exploitation is a matter of great con...In common practice in the oil fields,the injection of water and gas into reservoirs is a crucial technique to increase production.The control of the waterflooding front in oil/gas exploitation is a matter of great concern to reservoir engineers.Monitoring the waterflooding front in oil/gas wells plays a very important role in adjusting the well network and later in production,taking advantage of the remaining oil po-tential and ultimately achieving great success in improving the recovery rate.For a long time,micro-seismic monitoring,numerical simulation,four-dimensional seismic and other methods have been widely used in waterflooding front monitoring.However,reconciling their reliability and cost poses a significant challenge.In order to achieve real-time,reliable and cost-effective monitoring,we propose an innovative method for waterflooding front monitoring through the similarity analysis of passive source time-lapse seismic images.Typically,passive source seismic data collected from oil fields have extremely low signal-to-noise ratio(SNR),which poses a serious problem for obtaining structural images.The proposed method aims to visualize and analyze underground changes by highlighting time-lapse images and provide a strategy for underground monitoring using long-term passive source data under low SNR conditions.First,we verify the feasibility of the proposed method by designing a theoretical model.Then,we conduct an analysis of the correlation coefficient(similarity)on the passive source time-lapse seismic imaging results to enhance the image differences and identify the simulated waterflooding fronts.Finally,the proposed method is applied to the actual waterflooding front monitoring tasks in Shengli Oilfield,China.The research findings indicate that the monitoring results are consistent with the actual devel-opment conditions,which in turn demonstrates that the proposed method has great potential for practical application and is very suitable for monitoring common development tasks in oil fields.展开更多
Conventional time imaging techniques are not capable of producing accurate seismic imaging of the subsurface in the mountain front of the Tarim Basin, China. Their imaged structures have led to some major drilling fai...Conventional time imaging techniques are not capable of producing accurate seismic imaging of the subsurface in the mountain front of the Tarim Basin, China. Their imaged structures have led to some major drilling failures before, bearing a disrepute that ＂their structural closures have wheels and their structural highs have springs＂. This article first lists the imaging challenges, and explains in a schematic why the time imaging techniques fail in this area. Then through a series of real data examples, it demonstrates that when there exist lateral velocity variations, depth imaging is the only solution to tackle the imaging challenges in this area. Depth imaging accounts for the complexity of the wavefield, therefore produces superior and geological plausible images. The core task in properly performing depth imaging is building the velocity model. This article stresses some the main aspects in this regard.展开更多
The paper introduces the method of high-density seismic imaging exploration, discusses its features different from conventional shallow seismic reflection wave technique, and illustrates the application effect of the ...The paper introduces the method of high-density seismic imaging exploration, discusses its features different from conventional shallow seismic reflection wave technique, and illustrates the application effect of the method using three samples of engineering geological explorations on land and in water exploration of underground cavity, location survey of sunk ship and investigation of channel silt depth.展开更多
I present results of processing and structural interpretation of narrow-angle seismic reflection data recorded over an area of 30 × 50 km located in the southern part of the North Apuseni Mts, Romania. The invest...I present results of processing and structural interpretation of narrow-angle seismic reflection data recorded over an area of 30 × 50 km located in the southern part of the North Apuseni Mts, Romania. The investigated area is characterized by complex subsurface geology and rough topography. The seismic measurements were performed along five linear profiles, P1-P5, using an active spread of 96 geophones for each shot point;geophone spacing was 25 m. The length of each acquisition line is greater than 10 km. The signal-to-noise ratio of these data varies along the lines and its variation is considered to be an effect of rough topography, complex subsurface geology and varying surface conditions encountered during seismic data acquisition. The data processing was performed using a standard processing flow but with different processing parameters from one data set to another. I obtained five depth-converted migrated seismic sections after data processing. The accuracy of the depth values depends on that of the stacking velocities obtained from the velocity analyses performed on the filtered seismic data. Borehole information is not available, the investigated area belonging to the areas investigated for hydrocarbons. Each seismic section shows a different structural image of the subsurface and provides useful information about the tectonic and stratigraphic evolution of the investigated area. I obtained various structural images of the subsurface after the interpretation of the depth-converted migrated seismic sections, from a simple one with undeformed and inclined reflectors to a complex one with folded and faulted reflectors, especially the older ones. I interpreted intrusive bodies piercing through the overlying sediments, which are in good agreement with the results of older geophysical studies.展开更多
Yongle atoll in the Xisha(Paracel) Archipelago is an isolated carbonate platform developed on Precambrian metamorphic and Mesozoic volcanic rocks since the early Miocene. To identify the 3D stratigraphic architecture ...Yongle atoll in the Xisha(Paracel) Archipelago is an isolated carbonate platform developed on Precambrian metamorphic and Mesozoic volcanic rocks since the early Miocene. To identify the 3D stratigraphic architecture and evolution of this platform, 13 high-resolution seismic profiles and shallow-to-deep water multi-beam data were processed and analyzed to reveal seismic facies, sequence boundary reflectors, seismic units, and platform architecture. Nine types of seismic facies were recognized based on their geometry, which included seismic amplitude, continuity, and termination patterns;additionally, six reflections, i.e., Tg, T60, T50, T40, T30, and T20, were identified in the Cenozoic strata. Five seismic units, SQ1(lower Miocene), SQ2(middle Miocene), SQ3(upper Miocene), SQ4(Pliocene), and SQ5(Quaternary), were identified from bottom to top across the platform. The platform grew rapidly in the middle Miocene and backstepped in the late Miocene–Pliocene. Here, we discuss the developmental characteristics and evolution of the Yongle Atoll, in combination with drilling wells, which can be divided into four stages: the initiation stage in the early Miocene, the flourishing stage in the middle Miocene, the partial-drowning stage in the late Miocene–Pliocene, and modern atoll in the Quaternary.展开更多
In crosswell seismic exploration,the imaging section produced by migration based on a wave equation has a serious arc phenomenon at its edge and a small effective range because of geometrical restrictions.Another imag...In crosswell seismic exploration,the imaging section produced by migration based on a wave equation has a serious arc phenomenon at its edge and a small effective range because of geometrical restrictions.Another imaging section produced by the VSP-CDP stack imaging method employed with ray-tracing theory is amplitude-preserved.However,imaging 3D complex lithological structures accurately with this method is difficult.Therefore,this study proposes inverse Gaussian beam stack imaging in the 3D crosswell seismic exploration of deviated wells on the basis of Gaussian beam ray-tracing theory.By employing Gaussian beam ray-tracing theory in 3D crosswell seismic exploration,we analyzed the energy relationship between seismic wave fields and their effective rays.In imaging,the single-channel seismic wave fi eld data in the common shot point gather are converted into multiple effective wave fields in the common reflection point gather by the inverse Gaussian beam.The process produces a large fold number of intensive reflection points.Selected from the horizontal and vertical directions of the 2D measuring line,the wave fi elds of the eff ective reflection points in the same stack bin are projected onto the 2D measuring line,chosen according to the distribution characteristics of the reflection points,and stacked into an imaging section.The method is applied to X oilfi eld to identify the internal structure of the off shore gas cloud area.The results provided positive support for the inverse Gaussian beam stack imaging of 3D complex lithological structures and proved that technology is a powerful imaging tool for 3D crosswell seismic data processing.展开更多
The detailed structures of the plumbing system of the early Permian Tarim flood basalt were investigated by 3-D seismic imaging.The images show that the Tarim flood basalt mainly erupted from central volcanoes distrib...The detailed structures of the plumbing system of the early Permian Tarim flood basalt were investigated by 3-D seismic imaging.The images show that the Tarim flood basalt mainly erupted from central volcanoes distributed展开更多
Conventional seismic exploration,mostly based on reflection theory,hardly has accurate imaging results for disaster geologic bodies which have small scale,steep dip,or complex structure.In this paper,we design two typ...Conventional seismic exploration,mostly based on reflection theory,hardly has accurate imaging results for disaster geologic bodies which have small scale,steep dip,or complex structure.In this paper,we design two typical geologic models for analyzing the characteristics of scattered waves in mines for forward modeling by finite difference and apply the equivalent offset migration（EOM）and EOM-based interference stack migration methods to mine prospecting.We focus on the analysis of scatted imaging’s technological superiority to reflection imaging.Research shows：1）scattered imaging can improve fold and make the best of weak scattered information,so it shows better results than post-stack migration imaging and 2）it can utilize the diffraction stack migration method-based ray path theory for mine seismic advanced prediction,so it provides an new efficient imaging method for improving resolution of mine seismic exploration.展开更多
Passive image interferometry （PII） is becoming a powerful tool for detecting the temporal variations in the Earth＇s structure, which applies coda wave interferometry to the waveforrns from the cross-correlation of ...Passive image interferometry （PII） is becoming a powerful tool for detecting the temporal variations in the Earth＇s structure, which applies coda wave interferometry to the waveforrns from the cross-correlation of seismic ambient noise. There are four techniques for estimating temporal change of seismic velocity with PII： moving-window cross-correlation technique （MWCCT）, moving-window cross-spectrum technique （MWCST）, stretching technique （ST） and moving-window stretching technique （MWST）. In this paper, we use the continuous seismic records from a typical station pair near the Wenchuan Ms8.0 earthquake fault zone and generate three sets of waveforms by stacking cross-correlation function of ambient noise with different numbers of days, and then apply four techniques to processing the three sets of waveforms and compare their results. Our results indicate that the techniques based on moving-window （MWCCT, MWCST and MWST） are superior in detecting the change of seismic velocity, and the MWCST can give a better estimate of velocity change than the other moving-window techniques due to measurement error. We also investigate the clock errors and their influences on measuring velocity change. We find that when the clock errors are not very large, they have limited impact on the estimate of the velocity change with the moving-window techniques.展开更多
A common feature in seismic imageries of the crust and mantle is a layering pattern.Layering structures do exist in multiple scales,such as layered strata and unconformities in local and regional scales,and undulating...A common feature in seismic imageries of the crust and mantle is a layering pattern.Layering structures do exist in multiple scales,such as layered strata and unconformities in local and regional scales,and undulating seismic discontinuities in the crust and mantle.However,layering arti-fact also exists due to limitations in seismic processing and data coverage.There is a tendency for seis-mic stacking methods to over-map reflectors and scatters into along-isochron layers.In contrast,seis-mic tomography methods tend to under-map sub-horizontal layers with along-raypath smears and ar-tifacts of various de-mean processes.To better identify signals and artifacts in seismic imageries,it is necessary to understand the origins of various artifacts and make careful comparison between the solu-tions of different data and methods.展开更多
The Qinghai—Tibet plateau and its surrounding areas including Indian subcontinent, Xinjiang, Mongolia, is a largest lithosphere convergence place in the world, which characterized by continent\|continent collision wi...The Qinghai—Tibet plateau and its surrounding areas including Indian subcontinent, Xinjiang, Mongolia, is a largest lithosphere convergence place in the world, which characterized by continent\|continent collision with a thick crust and lithosphere. The high resolution seismic surface wave tomographic inversion has been conducted for studying the 3D velocity structure of crust and upper mantle in those areas. The seismic surface waveform data are from the archives of the CDSN, GSN and GEOSCOPE. About 2400 long period surface waveform recordings are available for both dispersion and waveform tomographic inversion. The block inversion by grid 1°×1°in Qinghai—Tibet plateau and 2°×2°in the surrounding areas were adapted. The resulting maps show the high resolution 3D shear wave velocity variation from earth’s surface to 400km depth.展开更多
基金supported by the National Natural Science Foundation of China(No.42374177)。
文摘Passive surface wave imaging has been a powerful tool for near-surface characterization in urban areas,which extracts surface wave signals from ambient seismic noise and then estimates subsurface shear wave velocity by inversion of the measured phase velocity.The high-frequency(approximately>1 Hz)seismic noise fields in urban environments are dominantly induced by human activities such as the vehicle traffic.Traffic seismic sources are nonrandomly distributed in time and space.Applying standard interferometric techniques to recordings from these nonrandom noise sources makes the Green’s function liable to estimation errors.We analyze the influence of using nonrandom traffic seismic sources for surface wave imaging.With nonrandom traffic seismic sources in time,spurious signals are generated in the cross-correlation function.With nonrandom traffic seismic sources in space,surface-wave phase velocities could be overestimated in the dispersion measurement.We provide an overview of solutions for surface-wave imaging with nonrandom traffic seismic sources in time and space,aiming to improve the retrieval of high-frequency surface waves and achieve reliable results from ultrashort(tens of seconds)observations for near-surface characterization.
文摘The conventional method of seismic data acquisition geometry design is based on the assumption of horizontal subsurface reflectors, which often is not suitable for complex structure. We start from a controlled illumination analysis and put forward a method of seismic survey geometry design for target-oriented imaging. The method needs a velocity model obtained by a preliminary seismic interpretation. The one-way Fourier finite-difference wave propagator is used to extrapolate plane wave sources on the target layer to the surface. By analyzing the wave energy distribution at the surface extrapolated from the target layer, the shot or receiver locations needed for target layer imaging can be determined. Numerical tests using the SEG-EAGE salt model suggest that this method is useful for confirming the special seismic acquisition geometry layout for target-oriented imaging.
基金supported by the R&D of Key Instruments and Technologies for Deep Resources Prospecting(No.ZDYZ2012-1)National Natural Science Foundation of China(No.11374322)
文摘Knowledge of the locations of seismic sources is critical for microseismic monitoring. Time-window-based elastic wave interferometric imaging and weighted- elastic-wave （WEW） interferometric imaging are proposed and used to locate modeled microseismic sources. The proposed method improves the precision and eliminates artifacts in location profiles. Numerical experiments based on a horizontally layered isotropic medium have shown that the method offers the following advantages： It can deal with Iow-SNR microseismic data with velocity perturbations as well as relatively sparse receivers and still maintain relatively high precision despite the errors in the velocity model. Furthermore, it is more efficient than conventional traveltime inversion methods because interferometric imaging does not require traveltime picking. Numerical results using a 2D fault model have also suggested that the weighted-elastic-wave interferometric imaging can locate multiple sources with higher location precision than the time-reverse imaging method.
基金The National Natural Science Foundation of China under contract Nos 41504084 and 41274120
文摘One of the problems experienced in marine geophysical exploration is that the layered features in the migration imaging profile are blurred and the seismic energy reflected is weaker in the middle or lower parts. In this study we model the seismic wavefield records in the undulating seafloor when there is both a slight change and significant change in seafloor topography to analyze its influence on the seismic reflection data and migration imaging profiles. We compare and analyze the wave field records collected at the same point on the original and modified velocity models, and the cross-bonding resulting migration imaging profiles. The results show that whether the seismic reflection data collection is performed along the direction of the survey line or against the direction of the survey line, slight changes in the seafloor topography have little effect on the wave field records and the migration profile, while significant changes in the seafloor topography have great effect on both the wave field records and migration profile.
基金Heterogeneous formation geophysical response characteristics (973 Program, subject number: 2007CB209601)Continental reservoir seismic physical model (CNPC Fundamental Research Projects, subject number: 06A10102)
文摘Acquisition footprint is a new concept to describe the seismic noise in three-dimensional seismic exploration and it is closely related to geometry and observation shuttering.At present,the study on acquisition footprints has become a hot spot.In partnership with the Dagang Oilfield,we used the channel sand body seismic physical model to study the characteristics of wide/narrow azimuth acquisition footprints and analyzed and compared the two types of footprints and their effects on target imaging.In addition,the footprints caused by data processing of the normal moveout offset(NMO)stretching aberration were discussed.These footprints are located only in the shallow or middle layer in the time slice,and possibly affect the imaging of shallow target layers,and have no influence on deep target imaging.Seismic physical modeling has its advantages in the study of acquisition footprints.
基金sponsored by the National Key R&D Plan Project(Grant No.2016YFC0303900)Natural Science Foundation of China(Grant No.41374145)
文摘To solve problems in small-scale and complex structural traps,the inverse Gaussian-beam stack-imaging method is commonly used to process crosswell seismic wave reflection data.Owing to limited coverage,the imaging quality of conventional ray-based crosswell seismic stack imaging is poor in complex areas;moreover,the imaging range is small and with sever interference because of the arc phenomenon in seismic migration.Thus,we propose the inverse Gaussian-beam stack imaging,in which Gaussian weight functions of rays contributing to the geophones energy are calculated and used to decompose the seismic wavefield.This effectively enlarges the coverage of the reflection points and improves the transverse resolution.Compared with the traditional VSP–CDP stack imaging,the proposed methods extends the imaging range,yields higher horizontal resolution,and is more adaptable to complex geological structures.The method is applied to model a complex structure in the K-area.The results suggest that the wave group of the target layer is clearer,the resolution is higher,and the main frequency of the crosswell seismic section is higher than that in surface seismic exploration The effectiveness and robustness of the method are verified by theoretical model and practical data.
基金a part of the joint Polish-Chinese FULLIMAGE project,which received funding in the SHENG call from National Natural Science Foundation of China(NSFC)under grant no.41961134001the Polish National Science Centre(NCN)under grant no.UMO-2018/30/Q/ST10/00680
文摘Active source seismic method is generally used to image subsurface structures for resource exploration,including oil,gas and coal.Although it can provide highresolution subsurface structures,due to some economic and environmental restrictions,it is not suitable in some cases.In recent 20 years,passive seismic survey based on ambient noise seismic interferometry(ANSI)has started to be widely used in imaging subsurface structures.In comparison,ANSI does not need active sources and can image subsurface structures at different depths as a lowcost alternative to active seismic exploration.
文摘As dense seismic arrays at different scales are deployed,the techniques to make full use of array data with low computing cost become increasingly needed.The wave gradiometry method(WGM)is a new branch in seismic tomography,which utilizes the spatial gradients of the wavefield to determine the phase velocity,wave propagation direction,geometrical spreading,and radiation pattern.Seismic wave propagation parameters obtained using the WGM can be further applied to invert 3D velocity models,Q values,and anisotropy at lithospheric(crust and/or mantle)and smaller scales(e.g.,industrial oilfield or fault zone).Herein,we review the theoretical foundation,technical development,and major applications of the WGM,and compared the WGM with other commonly used major array imaging methods.Future development of the WGM is also discussed.
基金This study was financially supported by the Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)(GML2019ZD0207)Dedicated Fund for Promoting High-Quality Economic Development in Guangdong Province(Marine Economic Development Project)(GDNRC[2020]045)the State Key Laboratory of Marine Geology of Tongji University(MGK202007).
文摘Shenhu area in South China Sea includes extensive collapse and diapir structures,forming high-angle faults and vertical fracture system,which functions as a fluid migration channel for gas hydrate formation.In order to improve the imaging precision of natural gas hydrate in this area,especially for fault and fracture structures,the present work propose a velocity stitching technique that accelerates effectively the convergence of the shallow seafloor,indicating seafloor horizon interpretation and the initial interval velocity for model building.In the depth domain,pre-stack depth migration and residual curvature are built into the model based on high-precision grid-tomography velocity inversion,after several rounds of tomographic iterations,as the residual velocity field converges gradually.Test results of the Shenhu area show that the imaging precision of the fault zone is obviously improved,the fracture structures appear more clearly,the wave group characteristics significantly change for the better and the signal-to-noise ratio and resolution are improved.These improvements provide the necessary basis for the new reservoir model and field drilling risk tips,help optimize the favorable drilling target,and are crucial for the natural gas resource potential evaluation.
基金supported by the CNPC-SWPU Innovation Alliance Technology Cooperation Project(2020CX020000)the National Natural Science Foundation of China(42022028)+1 种基金the Natural Science Foundation of Sichuan Province(24NSFSC0808)the China Scholarship Council(202306440144)。
文摘In common practice in the oil fields,the injection of water and gas into reservoirs is a crucial technique to increase production.The control of the waterflooding front in oil/gas exploitation is a matter of great concern to reservoir engineers.Monitoring the waterflooding front in oil/gas wells plays a very important role in adjusting the well network and later in production,taking advantage of the remaining oil po-tential and ultimately achieving great success in improving the recovery rate.For a long time,micro-seismic monitoring,numerical simulation,four-dimensional seismic and other methods have been widely used in waterflooding front monitoring.However,reconciling their reliability and cost poses a significant challenge.In order to achieve real-time,reliable and cost-effective monitoring,we propose an innovative method for waterflooding front monitoring through the similarity analysis of passive source time-lapse seismic images.Typically,passive source seismic data collected from oil fields have extremely low signal-to-noise ratio(SNR),which poses a serious problem for obtaining structural images.The proposed method aims to visualize and analyze underground changes by highlighting time-lapse images and provide a strategy for underground monitoring using long-term passive source data under low SNR conditions.First,we verify the feasibility of the proposed method by designing a theoretical model.Then,we conduct an analysis of the correlation coefficient(similarity)on the passive source time-lapse seismic imaging results to enhance the image differences and identify the simulated waterflooding fronts.Finally,the proposed method is applied to the actual waterflooding front monitoring tasks in Shengli Oilfield,China.The research findings indicate that the monitoring results are consistent with the actual devel-opment conditions,which in turn demonstrates that the proposed method has great potential for practical application and is very suitable for monitoring common development tasks in oil fields.
文摘Conventional time imaging techniques are not capable of producing accurate seismic imaging of the subsurface in the mountain front of the Tarim Basin, China. Their imaged structures have led to some major drilling failures before, bearing a disrepute that ＂their structural closures have wheels and their structural highs have springs＂. This article first lists the imaging challenges, and explains in a schematic why the time imaging techniques fail in this area. Then through a series of real data examples, it demonstrates that when there exist lateral velocity variations, depth imaging is the only solution to tackle the imaging challenges in this area. Depth imaging accounts for the complexity of the wavefield, therefore produces superior and geological plausible images. The core task in properly performing depth imaging is building the velocity model. This article stresses some the main aspects in this regard.
文摘The paper introduces the method of high-density seismic imaging exploration, discusses its features different from conventional shallow seismic reflection wave technique, and illustrates the application effect of the method using three samples of engineering geological explorations on land and in water exploration of underground cavity, location survey of sunk ship and investigation of channel silt depth.
文摘I present results of processing and structural interpretation of narrow-angle seismic reflection data recorded over an area of 30 × 50 km located in the southern part of the North Apuseni Mts, Romania. The investigated area is characterized by complex subsurface geology and rough topography. The seismic measurements were performed along five linear profiles, P1-P5, using an active spread of 96 geophones for each shot point;geophone spacing was 25 m. The length of each acquisition line is greater than 10 km. The signal-to-noise ratio of these data varies along the lines and its variation is considered to be an effect of rough topography, complex subsurface geology and varying surface conditions encountered during seismic data acquisition. The data processing was performed using a standard processing flow but with different processing parameters from one data set to another. I obtained five depth-converted migrated seismic sections after data processing. The accuracy of the depth values depends on that of the stacking velocities obtained from the velocity analyses performed on the filtered seismic data. Borehole information is not available, the investigated area belonging to the areas investigated for hydrocarbons. Each seismic section shows a different structural image of the subsurface and provides useful information about the tectonic and stratigraphic evolution of the investigated area. I obtained various structural images of the subsurface after the interpretation of the depth-converted migrated seismic sections, from a simple one with undeformed and inclined reflectors to a complex one with folded and faulted reflectors, especially the older ones. I interpreted intrusive bodies piercing through the overlying sediments, which are in good agreement with the results of older geophysical studies.
基金financially supported by Natural Science Foundation of China (U1701245)Research Program of Sanya Yazhou Bay Science and Technology City (No. SKJC-2020-01-009)+2 种基金Natural Science Foundation of China (91958206, 41876044)National Key Research and Development Program of China (2018YFC0308301)Strategic Priority Research Program of Chinese Academy of Sciences (XDA22040105)。
文摘Yongle atoll in the Xisha(Paracel) Archipelago is an isolated carbonate platform developed on Precambrian metamorphic and Mesozoic volcanic rocks since the early Miocene. To identify the 3D stratigraphic architecture and evolution of this platform, 13 high-resolution seismic profiles and shallow-to-deep water multi-beam data were processed and analyzed to reveal seismic facies, sequence boundary reflectors, seismic units, and platform architecture. Nine types of seismic facies were recognized based on their geometry, which included seismic amplitude, continuity, and termination patterns;additionally, six reflections, i.e., Tg, T60, T50, T40, T30, and T20, were identified in the Cenozoic strata. Five seismic units, SQ1(lower Miocene), SQ2(middle Miocene), SQ3(upper Miocene), SQ4(Pliocene), and SQ5(Quaternary), were identified from bottom to top across the platform. The platform grew rapidly in the middle Miocene and backstepped in the late Miocene–Pliocene. Here, we discuss the developmental characteristics and evolution of the Yongle Atoll, in combination with drilling wells, which can be divided into four stages: the initiation stage in the early Miocene, the flourishing stage in the middle Miocene, the partial-drowning stage in the late Miocene–Pliocene, and modern atoll in the Quaternary.
基金This research work is funded by the Scientific Research Program of Shaanxi Provincial Education Department(No.19JK0668)the Natural Science Basic Research Plan in Shaanxi Province of China(No.2021JQ-588).
文摘In crosswell seismic exploration,the imaging section produced by migration based on a wave equation has a serious arc phenomenon at its edge and a small effective range because of geometrical restrictions.Another imaging section produced by the VSP-CDP stack imaging method employed with ray-tracing theory is amplitude-preserved.However,imaging 3D complex lithological structures accurately with this method is difficult.Therefore,this study proposes inverse Gaussian beam stack imaging in the 3D crosswell seismic exploration of deviated wells on the basis of Gaussian beam ray-tracing theory.By employing Gaussian beam ray-tracing theory in 3D crosswell seismic exploration,we analyzed the energy relationship between seismic wave fields and their effective rays.In imaging,the single-channel seismic wave fi eld data in the common shot point gather are converted into multiple effective wave fields in the common reflection point gather by the inverse Gaussian beam.The process produces a large fold number of intensive reflection points.Selected from the horizontal and vertical directions of the 2D measuring line,the wave fi elds of the eff ective reflection points in the same stack bin are projected onto the 2D measuring line,chosen according to the distribution characteristics of the reflection points,and stacked into an imaging section.The method is applied to X oilfi eld to identify the internal structure of the off shore gas cloud area.The results provided positive support for the inverse Gaussian beam stack imaging of 3D complex lithological structures and proved that technology is a powerful imaging tool for 3D crosswell seismic data processing.
文摘The detailed structures of the plumbing system of the early Permian Tarim flood basalt were investigated by 3-D seismic imaging.The images show that the Tarim flood basalt mainly erupted from central volcanoes distributed
基金supported financially by the National Key Project(Grant No.2008ZX05035)the 973 Program(Grant No. 2009CB219603 and 2007CB209406)the National Natural Science Foundation of China(Grant No.50974081)
文摘Conventional seismic exploration,mostly based on reflection theory,hardly has accurate imaging results for disaster geologic bodies which have small scale,steep dip,or complex structure.In this paper,we design two typical geologic models for analyzing the characteristics of scattered waves in mines for forward modeling by finite difference and apply the equivalent offset migration（EOM）and EOM-based interference stack migration methods to mine prospecting.We focus on the analysis of scatted imaging’s technological superiority to reflection imaging.Research shows：1）scattered imaging can improve fold and make the best of weak scattered information,so it shows better results than post-stack migration imaging and 2）it can utilize the diffraction stack migration method-based ray path theory for mine seismic advanced prediction,so it provides an new efficient imaging method for improving resolution of mine seismic exploration.
基金supported by National Natural Science Foundation of China (No. 41074061)Basic Research Plan of the Institute of Earthquake Science, China Earthquake Administration (No. 2007-13)
文摘Passive image interferometry （PII） is becoming a powerful tool for detecting the temporal variations in the Earth＇s structure, which applies coda wave interferometry to the waveforrns from the cross-correlation of seismic ambient noise. There are four techniques for estimating temporal change of seismic velocity with PII： moving-window cross-correlation technique （MWCCT）, moving-window cross-spectrum technique （MWCST）, stretching technique （ST） and moving-window stretching technique （MWST）. In this paper, we use the continuous seismic records from a typical station pair near the Wenchuan Ms8.0 earthquake fault zone and generate three sets of waveforms by stacking cross-correlation function of ambient noise with different numbers of days, and then apply four techniques to processing the three sets of waveforms and compare their results. Our results indicate that the techniques based on moving-window （MWCCT, MWCST and MWST） are superior in detecting the change of seismic velocity, and the MWCST can give a better estimate of velocity change than the other moving-window techniques due to measurement error. We also investigate the clock errors and their influences on measuring velocity change. We find that when the clock errors are not very large, they have limited impact on the estimate of the velocity change with the moving-window techniques.
基金supported by the National Natural Science Foundation of China (No. 40730317)
文摘A common feature in seismic imageries of the crust and mantle is a layering pattern.Layering structures do exist in multiple scales,such as layered strata and unconformities in local and regional scales,and undulating seismic discontinuities in the crust and mantle.However,layering arti-fact also exists due to limitations in seismic processing and data coverage.There is a tendency for seis-mic stacking methods to over-map reflectors and scatters into along-isochron layers.In contrast,seis-mic tomography methods tend to under-map sub-horizontal layers with along-raypath smears and ar-tifacts of various de-mean processes.To better identify signals and artifacts in seismic imageries,it is necessary to understand the origins of various artifacts and make careful comparison between the solu-tions of different data and methods.
文摘The Qinghai—Tibet plateau and its surrounding areas including Indian subcontinent, Xinjiang, Mongolia, is a largest lithosphere convergence place in the world, which characterized by continent\|continent collision with a thick crust and lithosphere. The high resolution seismic surface wave tomographic inversion has been conducted for studying the 3D velocity structure of crust and upper mantle in those areas. The seismic surface waveform data are from the archives of the CDSN, GSN and GEOSCOPE. About 2400 long period surface waveform recordings are available for both dispersion and waveform tomographic inversion. The block inversion by grid 1°×1°in Qinghai—Tibet plateau and 2°×2°in the surrounding areas were adapted. The resulting maps show the high resolution 3D shear wave velocity variation from earth’s surface to 400km depth.
