Amplitude‐offset relationships over shallow velocity inversions

Geophysics ◽  
1989 ◽  
Vol 54 (9) ◽  
pp. 1114-1122 ◽  
Author(s):  
D. F. Poley ◽  
D. C. Lawton ◽  
S. M. Blasco
Keyword(s):  
High Resolution ◽  
Ray Tracing ◽  
Seismic Data ◽  
Energy Partitioning ◽  
Velocity Analysis ◽  
Zoeppritz Equations ◽  
Reflection Data ◽  
Offset Distance ◽  
Phase Variations ◽  
Selection Of

The amplitude and phase of reflected seismic data can vary significantly with the offset distance between source and receiver. Analysis of amplitude‐offset relationships in high‐resolution seismic data from areas of shallow permafrost in the Beaufort Sea is undertaken in this paper. Reflection attributes produced by energy partitioning at interfaces under nonnormal angles of incidence were studied by means of ray tracing and the Zoeppritz equations. Observed amplitude and phase variations were found to cause CDP stacking techniques to degrade reflection data quality, particularly where the zone of interest features velocity inversions or is shallow in relation to receiver lengths. In these cases velocity analysis based on coherency measures may result in the selection of incorrect stacking velocities.

Late Cretaceous – Cenozoic history of the transition zone between the East European Craton and the Paleozoic Platform, Polish sector of the Baltic Sea, revealed by new offshore regional seismic reflection data (BALTEC project)

2021 ◽  
Author(s):  
Piotr Krzywiec ◽  
Łukasz Słonka ◽  
Quang Nguyen ◽  
Michał Malinowski ◽  
Mateusz Kufrasa ◽  
...  
Keyword(s):  
High Resolution ◽  
Late Cretaceous ◽  
Seismic Data ◽  
Seismic Reflection ◽  
Upper Cretaceous ◽  
Seismic Reflection Data ◽  
East European ◽  
Reflection Data ◽  
Multichannel Seismic Reflection ◽  
Multichannel Seismic Reflection Data

<p>In 2016, approximately 850 km of high-resolution multichannel seismic reflection data of the BALTEC survey have been acquired offshore Poland within the transition zone between the East European Craton and the Paleozoic Platform. Data processing, focused on removal of multiples, strongly overprinting geological information at shallower intervals, included SRME, TAU-P domain deconvolution, high resolution parabolic Radon demultiple and SWDM (Shallow Water De-Multiple). Entire dataset was Kirchhoff pre-stack time migrated. Additionally, legacy shallow high-resolution multichannel seismic reflection data acquired in this zone in 1997 was also used. All this data provided new information on various aspects of the Phanerozoic evolution of this area, including Late Cretaceous to Cenozoic tectonics and sedimentation. This phase of geological evolution could be until now hardly resolved by analysis of industry seismic data as, due to limited shallow seismic imaging and very strong overprint of multiples, essentially no information could have been retrieved from this data for first 200-300 m. Western part of the BALTEC dataset is located above the offshore segment of the Mid-Polish Swell (MPS) – large anticlinorium formed due to inversion of the axial part of the Polish Basin. BALTEC seismic data proved that Late Cretaceous inversion of the Koszalin – Chojnice fault zone located along the NE border of the MPS was thick-skinned in nature and was associated with substantial syn-inversion sedimentation. Subtle thickness variations and progressive unconformities imaged by BALTEC seismic data within the Upper Cretaceous succession in vicinity of the Kamień-Adler and the Trzebiatów fault zones located within the MPS documented complex interplay of Late Cretaceous basin inversion, erosion and re-deposition. Precambrian basement of the Eastern, cratonic part of the study area is overlain by Cambro-Silurian sedimentary cover. It is dissected by a system of steep, mostly reverse faults rooted in most cases in the deep basement. This fault system has been regarded so far as having been formed mostly in Paleozoic times, due to the Caledonian orogeny. As a consequence, Upper Cretaceous succession, locally present in this area, has been vaguely defined as a post-tectonic cover, locally onlapping uplifted Paleozoic blocks. New seismic data, because of its reliable imaging of the shallowest substratum, confirmed that at least some of these deeply-rooted faults were active as a reverse faults in latest Cretaceous – earliest Paleogene. Consequently, it can be unequivocally proved that large offshore blocks of Silurian and older rocks presently located directly beneath the Cenozoic veneer must have been at least partly covered by the Upper Cretaceous succession; then, they were uplifted during the widespread inversion that affected most of Europe. Ensuing regional erosion might have at least partly provided sediments that formed Upper Cretaceous progradational wedges recently imaged within the onshore Baltic Basin by high-end PolandSPAN regional seismic data. New seismic data imaged also Paleogene and younger post-inversion cover. All these results prove that Late Cretaceous tectonics substantially affected large areas located much farther towards the East than previously assumed.</p><p>This study was funded by the Polish National Science Centre (NCN) grant no UMO-2017/27/B/ST10/02316.</p>

Poststack velocity analysis by separation and imaging of seismic diffractions

Geophysics ◽  
2007 ◽  
Vol 72 (6) ◽  
pp. U89-U94 ◽  
Author(s):  
Sergey Fomel ◽  
Evgeny Landa ◽  
M. Turhan Taner
Keyword(s):  
High Resolution ◽  
Seismic Data ◽  
Field Data ◽  
Small Scale ◽  
Velocity Analysis ◽  
High Resolution Imaging ◽  
Diffracted Waves ◽  
Resolution Imaging ◽  
Seismic Reflections ◽  
Optimal Focusing

Small geologic features manifest themselves in seismic data in the form of diffracted waves, which are fundamentally different from seismic reflections. Using two field-data examples and one synthetic example, we demonstrate the possibility of separating seismic diffractions in the data and imaging them with optimally chosen migration velocities. Our criteria for separating reflection and diffraction events are the smoothness and continuity of local event slopes that correspond to reflection events. For optimal focusing, we develop the local varimax measure. The objectives of this work are velocity analysis implemented in the poststack domain and high-resolution imaging of small-scale heterogeneities. Our examples demonstrate the effectiveness of the proposed method for high-resolution imaging of such geologic features as faults, channels, and salt boundaries.

scholarly journals High-resolution coherency functionals for velocity analysis: An application for subbasalt seismic exploration

Geophysics ◽  
2013 ◽  
Vol 78 (5) ◽  
pp. U53-U63 ◽  
Author(s):  
Andrea Tognarelli ◽  
Eusebio Stucchi ◽  
Alessia Ravasio ◽  
Alfredo Mazzotti
Keyword(s):  
High Resolution ◽  
Seismic Data ◽  
Field Data ◽  
Signal To Noise Ratio ◽  
Synthetic Seismograms ◽  
Seismic Exploration ◽  
Velocity Analysis ◽  
Signal To Noise ◽  
Geologic Setting ◽  
Analytic Signals

We tested the properties of three different coherency functionals for the velocity analysis of seismic data relative to subbasalt exploration. We evaluated the performance of the standard semblance algorithm and two high-resolution coherency functionals based on the use of analytic signals and of the covariance estimation along hyperbolic traveltime trajectories. Approximate knowledge of the wavelet was exploited to design appropriate filters that matched the primary reflections, thereby further improving the ability of the functionals to highlight the events of interest. The tests were carried out on two synthetic seismograms computed on models reproducing the geologic setting of basaltic intrusions and on common midpoint gathers from a 3D survey. Synthetic and field data had a very low signal-to-noise ratio, strong multiple contamination, and weak primary subbasalt signals. The results revealed that high-resolution coherency functionals were more suitable than semblance algorithms to detect primary signals and to distinguish them from multiples and other interfering events. This early discrimination between primaries and multiples could help to target specific signal enhancement and demultiple operations.

Image Processing Based on Improved Signal Estimation Algorithm

2013 ◽  
Vol 373-375 ◽  
pp. 694-697 ◽  
Author(s):  
Guang Xun Chen ◽  
Yan Hui Du ◽  
Lei Zhang ◽  
Pan Ke Qin
Keyword(s):  
Image Processing ◽  
High Resolution ◽  
Energy Function ◽  
Seismic Data ◽  
Estimation Algorithm ◽  
Numerical Realization ◽  
Velocity Analysis ◽  
Signal Estimation ◽  
Seismic Data Processing ◽  
Improved Method

The commonly used method for high resolution velocity analysis in seismic data processing and interpreting is based on signal estimation algorithm. However, the numerical realization of this method is complicated and time-consuming due to the process of signal-noise separation requiring enormous loop calculations before constructing the energy function. In this paper, we improved the method on the base of multi-trace signal estimation. This improved method made full use of amplitude information that can enhance the anti-noise ability and improve the resolution greatly. Meanwhile, this method has more economical calculation cost than other methods for it didnt require multiple loop calculations.

High-resolution seismic velocity analysis as a tool for exploring gas hydrate systems: An example from New Zealand’s southern Hikurangi margin

2016 ◽  
Vol 4 (1) ◽  
pp. SA1-SA12 ◽  
Author(s):  
Gareth J. Crutchley ◽  
Guy Maslen ◽  
Ingo A. Pecher ◽  
Joshu J. Mountjoy
Keyword(s):  
High Resolution ◽  
Marine Sediments ◽  
Gas Hydrate ◽  
Seismic Data ◽  
Seismic Velocity ◽  
Coarse Grained ◽  
Velocity Analysis ◽  
Low Velocity ◽  
Free Gas ◽  
Velocity Models

The existence of free gas and gas hydrate in the pore spaces of marine sediments causes changes in acoustic velocities that overprint the background lithological velocities of the sediments themselves. Much previous work has determined that such velocity overprinting, if sufficiently pronounced, can be resolved with conventional velocity analysis from long-offset, multichannel seismic data. We used 2D seismic data from a gas hydrate province at the southern end of New Zealand’s Hikurangi subduction margin to describe a workflow for high-resolution velocity analysis that delivered detailed velocity models of shallow marine sediments and their coincident gas hydrate systems. The results showed examples of pronounced low-velocity zones caused by free gas ponding beneath the hydrate layer, as well as high-velocity zones related to gas hydrate deposits. For the seismic interpreter of a gas hydrate system, the velocity results represent an extra “layer” for interpretation that provides important information about the distribution of free gas and gas hydrate. By combining the velocity information from the seismic transect with geologic samples of the seafloor and an understanding of sedimentary processes, we have determined that high gas hydrate concentrations preferentially form within coarse-grained sediments at the proximal end of the Hikurangi Channel. Finer grained sediments expected elsewhere along the seismic transect might preclude the deposition of similarly high gas hydrate concentrations away from the channel.

Mirror reverse time migration using vertical cable seismic data for methane hydrate exploration

Geophysics ◽  
2019 ◽  
Vol 84 (6) ◽  
pp. B447-B460
Author(s):  
Ehsan Jamali H. ◽  
Masafumi Katou ◽  
Kenji Tara ◽  
Eiichi Asakawa ◽  
Hitoshi Mikada
Keyword(s):  
High Resolution ◽  
Seismic Data ◽  
Methane Hydrate ◽  
The Sea Of Japan ◽  
Velocity Analysis ◽  
Reverse Time ◽  
Reverse Time Migration ◽  
Time Migration ◽  
Shallow Sediments

Gas hydrates are located in the permafrost and in deepwater shallow sediments, where low temperature and high pressure satisfy the stability conditions of methane clathrates to remain as solid compounds. Hydrates are found in a form of fine-layered or altered-layered structure with hiatuses and necessitate high-resolution surveys, which may not be achieved by conventional marine acquisition using towed streamers. We have developed a recent case study in which the vertical cable seismic (VCS) method has been used for high-resolution subseafloor imaging using a set of buoyed vertical-arrayed receivers that are anchored to the seafloor. The observation close to the target in the deepwater environment provides a higher signal-to-noise ratio and higher resolution. The primary reflections, however, could not achieve reliable depth images in the data processing due to their limited subsurface coverage. We used a reverse time migration (RTM) implementation of mirror imaging to extend the spatial subsurface coverage by using receiver ghost reflections. Because conventional velocity analysis methods are not applicable to the VCS survey due to the asymmetrical reflection path between the source and receiver, we implemented seismic interferometry and generated virtual surface seismic data from VCS data for velocity analysis. To preserve the resolution, amplitudes, and phase characteristics, we applied mirror RTM on the ghost reflections in the original VCS data rather than imaging the virtual data. The introduced case study using a VCS survey for identifying the methane hydrate system of the Umitaka Spur in the Sea of Japan led to high-resolution images, which suggest that a large gas chimney exists beneath a pockmark and is responsible for transferring methane gas from a deep hydrocarbon source to the shallow sediments. A bottom-simulating reflector as the base of the gas hydrate stability zone was also imaged.

New insights into North Sea tunnel valley infill and genesis from high-resolution 3D seismic data

2020 ◽  
Author(s):  
James Kirkham ◽  
Kelly Hogan ◽  
Robert Larter ◽  
Ed Self ◽  
Ken Games ◽  
...  
Keyword(s):  
High Resolution ◽  
North Sea ◽  
Seismic Data ◽  
3D Seismic ◽  
Seismic Reflection Data ◽  
North West ◽  
The North ◽  
Reflection Data ◽  
Order Of Magnitude ◽  
Subglacial Meltwater

<p>Tunnel valleys are large (kilometres wide, hundreds of metres deep) channels incised into bedrock and soft sediments by the action of pressurised subglacial meltwater. Discovered over a century ago, they are common across large swathes of North-West Europe and North America. However, many aspects of tunnel valley formation, and the processes by which they are infilled, remain poorly understood. Here, we use new high-resolution 3D seismic reflection data, collected by the geohazard assessment industry, to examine the infill lithology and architecture of buried tunnel valleys located in the central North Sea. The spatial resolution of our seismic data (3.125-6.25 m bin size) represents an order of magnitude improvement in the data resolution that has previously been used to study tunnel valleys in this region, allowing us to examine their infill in unprecedented detail. Inside the tunnel valleys, we identify a suite of buried subglacial landforms, some of which have rarely been reported inside tunnel valleys before. These landforms include a 14-km-long system of segmented eskers, crevasse-squeeze ridges, subsidiary meltwater channels and retreat moraines. Their presence suggests that, in some cases, tunnel valleys in the North Sea were reoccupied by ice following their initial formation, casting doubt on hypotheses which invoke catastrophic releases of water to explain tunnel valley creation.</p>

Automatic velocity analysis using high-resolution hyperbolic Radon transform

Geophysics ◽  
2018 ◽  
Vol 83 (4) ◽  
pp. A53-A57 ◽  
Author(s):  
Yangkang Chen
Keyword(s):  
High Resolution ◽  
Radon Transform ◽  
Seismic Data ◽  
Optimization Problem ◽  
Least Squares Method ◽  
Velocity Model ◽  
Velocity Spectrum ◽  
Velocity Analysis ◽  
Hard Constraint ◽  
Reflection Seismic

Velocity analysis is crucial in reflection seismic data processing and imaging. Velocity picking is widely used in the industry for building the initial velocity model. When the size of the seismic data becomes extremely large, we cannot afford the corresponding human endeavor that is required by the velocity picking. In such situations, an automatic velocity-picking algorithm is highly demanded. We have developed a novel automatic velocity-analysis algorithm that is based on the high-resolution hyperbolic Radon transform. We formulate the automatic velocity-analysis problem as a constrained optimization problem. To solve the optimization problem with a hard constraint on the sparsity and distribution of the velocity spectrum, we relax it to a more familiar L1-regularized optimization problem in two steps. We use the iterative preconditioned least-squares method to solve the L1-regularized problem, and then we apply the hard constraint of the target optimization during the iterative inversion. Using synthetic and field-data examples, we determine the successful performance of our algorithm.

High‐resolution seismic study in the Gas Hills uranium district, Wyoming

Geophysics ◽  
1982 ◽  
Vol 47 (10) ◽  
pp. 1355-1374
Author(s):  
James K. Applegate ◽  
David A. Emilia ◽  
Edwin B. Neitzel ◽  
Paul R. Donaldson
Keyword(s):  
High Resolution ◽  
Seismic Data ◽  
Seismic Reflection ◽  
Three Dimensional ◽  
Synthetic Seismograms ◽  
Seismic Reflection Data ◽  
Structural Controls ◽  
Reflection Data ◽  
Passive Seismic ◽  
Channel Deposits

A study was undertaken to evaluate the effectiveness of the high‐resolution seismic technique for the mapping of stratigraphic and structural controls in the Gas Hills uranium district, Wyoming. The test area is one in which uranium deposits are in Tertiary sediments which unconformably overlie a Mesozoic Paleozoic section. Paleochannels on the unconformity appear to control the localization of the uranium. Drilling in the area allows an evaluation of the effectiveness of the study. Using both sonic and density logs, we computed synthetic seismograms to evaluate the feasibility of predicting the success of the seismic reflection technique and to test this prediction using surface seismic methods. The field study was undertaken utilizing primarily two energy sources—a high‐frequency vibrator (40–350 Hz), and one‐pound dynamite charges shot in 10-ft holes. A limited amount of data was also acquired using detonating cord on the surface. Some three‐dimensional (3-D) data were also acquired, and a later study acquired passive seismic data. The seismic reflection data were successful not only in delineating the unconformable surface and in mapping paleodrainages on the unconformity, but also in defining channel deposits within the Tertiary section. Correlation with the logs shows the success of the study. Several areas were delineated where one would undertake tight drilling patterns, and other areas were delineated in which one might minimize or eliminate exploratory drilling. The synthetic seismograms also could have predicted the success of the seismic work.

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