scholarly journals Attenuation of Seismic Multiples in Very Shallow Water: An Application in Archaeological Prospection Using Data Driven Approaches

2021 ◽  
Vol 13 (10) ◽  
pp. 1871
Author(s):  
Michaela Schwardt ◽  
Dennis Wilken ◽  
Wolfgang Rabbel
Keyword(s):  
Shallow Water ◽  
Field Data ◽  
Water Layer ◽  
Primary Energy ◽  
Time Shift ◽  
Multiple Reflections ◽  
Traditional Methods ◽  
Near Surface ◽  
Archaeological Prospection ◽  
Model Driven

Water-layer multiples pose a major problem in shallow water seismic investigations as they interfere with primaries reflected from layer boundaries or archaeology buried only a few meters below the water bottom. In the present study we evaluate two model-driven approaches (“Prediction and Subtraction” and “RTM-Deco”) to attenuate water-layer multiple reflections in very shallow water using synthetic and field data. The tests comprise both multi- and constant-offset data. We compare the multiple removal efficiency of the evaluated methods with two traditional methods (Predictive Deconvolution and SRME). Both model-driven approaches yield satisfactory results concerning the enhancement of primary energy and the attenuation of multiple energy. For the synthetic test cases, the multiple energy is reduced by at least 80% for the Prediction and Subtraction approach, and by more than 60% for the RTM-Deco approach. The application to two field data sets shows a significant amplification of primaries formerly hidden by the first water-layer multiple, with a reduction of multiple energy of up to 50%. The waveforms obtained from FD modeling match the true waveforms of the field data well and small deviations in time and amplitude can be removed by a time shift of the traces as well as an amplitude adaption to the field data. The field data examples should be emphasized, where the tested Prediction and Subtraction approach works significantly better than the traditional methods: the multiples are effectively predicted and attenuated while primary signals are highlighted. In conclusion, this shows that this method is particularly suitable in shallow water applications. Both evaluated multiple attenuation approaches could be successfully transferred to two other 3D systems used in shallow water near surface investigations. Especially the Prediction and Subtraction approach is able to enhance the primaries for both tested 3D systems with the multiple energy being reduced by more than 50%.

scholarly journals Theoretical Model of Acoustic Wave Propagation in Shallow Water

2017 ◽  
Vol 24 (2) ◽  
pp. 48-55 ◽  
Author(s):  
Eugeniusz Kozaczka ◽  
Grażyna Grelowska
Keyword(s):  
Shallow Water ◽  
Acoustic Field ◽  
Acoustic Waves ◽  
Sound Propagation ◽  
Low Frequency ◽  
Water Layer ◽  
Surface Shape ◽  
Shallow Sea ◽  
Multiple Reflections ◽  
Indirect Determination

Abstract The work is devoted to the propagation of low frequency waves in a shallow sea. As a source of acoustic waves, underwater disturbances generated by ships were adopted. A specific feature of the propagation of acoustic waves in shallow water is the proximity of boundaries of the limiting media characterised by different impedance properties, which affects the acoustic field coming from a source situated in the water layer “deformed” by different phenomena. The acoustic field distribution in the real shallow sea is affected not only by multiple reflections, but also by stochastic changes in the free surface shape, and statistical changes in the seabed shape and impedance. The paper discusses fundamental problems of modal sound propagation in the water layer over different types of bottom sediments. The basic task in this case was to determine the acoustic pressure level as a function of distance and depth. The results of the conducted investigation can be useful in indirect determination of the type of bottom.

Training deep networks with only synthetic data: Deep-learning-based near-offset reconstruction for closed-loop surface-related multiple estimation on shallow-water field data

Geophysics ◽  
2021 ◽  
pp. 1-32
Author(s):  
Shan Qu ◽  
Eric Verschuur ◽  
Dong Zhang ◽  
Yangkang Chen
Keyword(s):  
Deep Learning ◽  
Shallow Water ◽  
Network Architecture ◽  
Field Data ◽  
Closed Loop ◽  
Waveform Inversion ◽  
Synthetic Data ◽  
Water Layer ◽  
Limited Information ◽  
Loop Surface

Accurate removal of surface-related multiples remains a challenge in shallow-water cases. One reason is that the success of the surface-related multiple estimation (SRME) related algorithms is sensitive to the quality of the near-offset reconstruction. When it comes to a larger missing gap and a shallower water-bottom, the state-of-the-art near-offset gap construction method — parabolic Radon transform (PRT) — fails to provide a reliable recovery of the shallow reflections due to the limited information from the data and highly curved events at near offsets with strong lateral amplitude variations. Therefore, we propose a novel workflow, which first deploys a deep-learning(DL)-based reconstruction of the shallow reflections and then uses the reconstructed data as the input for the subsequent surface multiple removal. In particular, we use a convolutional neural network architecture --- U-net, which was developed from convolutional autoencoders with extra direct skip connections between different levels of encoders and the corresponding decoders. Instead of using field data directly in network training, the training set is carefully synthesized based on the prior water-layer information of the field data; thus, a fully sampled field dataset, which is hard to obtain, is not needed for training in the proposed workflow. An inversion-based approach — closed-loop surface-related multiple estimation (CL-SRME) -- is used for the surface multiple removal, in which the primaries are directly estimated via full waveform inversion in a data-driven manner. Finally, the effectiveness of the proposed workflow is demonstrated based on a 2D North Sea field data in a shallow-water scenario (92.5 m water depth) with a relatively large minimum offset (150 m).

Computer Application in Geosciences: Imaging of the Subsurface by Structural Coupled Inversion of Potential Field Data

2014 ◽  
Vol 644-650 ◽  
pp. 2670-2673
Author(s):  
Jun Wang ◽  
Xiao Hong Meng ◽  
Fang Li ◽  
Jun Jie Zhou
Keyword(s):  
Potential Field ◽  
Field Data ◽  
Gravity Data ◽  
Computer Application ◽  
Magnetic Data ◽  
Imaging Method ◽  
Inversion Algorithm ◽  
Constant Property ◽  
Near Surface ◽  
Potential Field Data

With the continuing growth in influence of near surface geophysics, the research of the subsurface structure is of great significance. Geophysical imaging is one of the efficient computer tools that can be applied. This paper utilize the inversion of potential field data to do the subsurface imaging. Here, gravity data and magnetic data are inverted together with structural coupled inversion algorithm. The subspace (model space) is divided into a set of rectangular cells by an orthogonal 2D mesh and assume a constant property (density and magnetic susceptibility) value within each cell. The inversion matrix equation is solved as an unconstrained optimization problem with conjugate gradient method (CG). This imaging method is applied to synthetic data for typical models of gravity and magnetic anomalies and is tested on field data.

scholarly journals Result of modeling temperature anomalies on the water surface of the research basin of the institute of hydromechanics NAS of Ukraine

2018 ◽  
pp. 40-45
Author(s):  
Oleksandr Fedorovsky ◽  
Vitalii Filimonov ◽  
Iryna Piestova ◽  
Stanislav Dugin ◽  
Vladyslav Yakymchuk ◽  
...  
Keyword(s):  
Water Surface ◽  
Water Layer ◽  
Sea Surface ◽  
National Academy Of Sciences ◽  
Near Surface ◽  
Aerial Photos ◽  
Temperature Anomalies ◽  
Structural And Textural Parameters ◽  
The Difference ◽  
Hydrocarbon Deposits

The results of the research and physical modeling of temperature anomalies of natural or man-made origin on the water surface are presented.  The information for the research was obtained from the experimental basin of the Institute of Hydromechanics of the National Academy of Sciences of Ukraine from the self-propelled model as the generator of hydrodynamic processes. The information obtained after image processing allowed to significantly expand the existing ideas about the mechanism of formation of anomalies on the open surface with the hydrodynamic disturbances from hydrocarbon deposits and moving submerged object. The interaction of the emerging hydrodynamic disturbances with the near-surface water layer and the occurrence of unmasking temperature anomalies on the open sea surface have a lot in common between the hydrocarbon deposits and the moving submerged object. The application of the difference of the above structural and textural parameters by calculating the value of "entropy" has been proposed as the informative feature for decoding the images of the water surface with the presence of hydrocarbon deposits or moving immersed objects. The decoding of temperature anomalies consists of two stages: learning and proper decoding. The first stage is the supervised learning, during which the system is being researched using the existing set of images, in which only the background and no hydrocarbon deposits or moving submerged object. Training is carried out in order to determine the signs of belonging to the background or hydrocarbon deposits, moving submerged object. It was determined that the background has minimal entropy values, and with the appearance of an anomaly, the entropy grows to the maximum value, after which, as the temperature trace dissipates, it begins to fall to background values. This confirms the informativity of the entropy feature for decoding the optical anomalies of man-made and natural origin on the sea surface from aerial photos.

scholarly journals On the changes in the sea surface temperature in the Benguela upwelling region. Part 1: season cycle

2019 ◽  
pp. 33-44
Author(s):  
A. B. Polonsky ◽  
A. N. Serebrennikov
Keyword(s):  
Surface Temperature ◽  
Seasonal Variability ◽  
Surface Wind ◽  
Water Layer ◽  
Hydrodynamic Characteristics ◽  
Entire Area ◽  
Near Surface ◽  
Sea Level Anomalies ◽  
Benguela Upwelling ◽  
Upwelling Index

Based on daily ocean surface temperature values for 1982–2017, near-surface wind for 1988–2017. and sea level anomalies for 1993–2017, obtained from satellite data, the seasonal variability of the hydrodynamic characteristics of the upper water layer in the vicinity of the Benguela upwelling is investigated. It is shown that the thermal upwelling index averaged over the entire area with lower temperature values does not give a correct idea on the seasonal course of the water lifting rate in the upwelling zone due to the significant horizontal advection of waters of upwelling origin. The seasonal variations of the vertical velocity of wind origin in the Benguela upwelling zone are characterized by the presence of two extremes from October to March, which is manifested in the predominance of the semiannual harmonic. At the same time, the thermal upwelling index in the zone of distribution of upwelling waters is subject to seasonal variability with an annual period.

Overcoming the challenges of a shallow-water sparse wide-azimuth survey to improve deep reservoir imaging in the East China Sea

2019 ◽  
Vol 38 (8) ◽  
pp. 610-616
Author(s):  
Yun Wei ◽  
Hua Chen ◽  
Senqing Hu ◽  
Peipei Deng ◽  
Yongdeng Xiao ◽  
...  
Keyword(s):  
Shallow Water ◽  
East China Sea ◽  
Three Dimensional ◽  
Water Layer ◽  
Velocity Model ◽  
East China ◽  
The East China Sea ◽  
China Sea ◽  
Well Data ◽  
The Impact

A new broadband wide-azimuth towed-streamer (WATS) survey was acquired to better resolve reservoir compartments in a shallow-water region of the East China Sea. To offset the shortcomings of narrow-azimuth acquisition along the strike direction, two vessels were added side-by-side as additional source vessels to form the WATS acquisition geometry for this survey. This WATS acquisition was much sparser than typical WATS surveys used in deepwater environments due to its one-sided configuration. The combination of sparse acquisition, shallow water, and deep targets set the challenge of how to optimally reveal the potential of side-gun data to improve the final image. Three-dimensional effects and severe aliasing in the crossline direction pose significant challenges for side-gun data processing. We present a comprehensive workflow to resolve these challenges consisting of 3D deghosting, 3D model-based water-layer demultiple, 3D surface-related multiple elimination, and 4D regularization for sparse and shallow-water wide-azimuth data. A tilted orthorhombic velocity model is built with better constraints from the wide-azimuth data, leading to improved fault positioning and imaging. Side-gun data clearly enhance the final target reservoir image and tie better with well data due to improved illumination. A new channel is discovered based on interpretation from the inverted VP/VS, explaining the previous incorrect prediction for one failed well that was drilled into a thinner and shallower channel unconnected to the main reservoir. An analysis of the impact of side-gun data from different offsets and azimuths shows that better azimuthal distribution within middle offset ranges had a more significant impact than far offsets in the final image of this survey. This information provides valuable reference in similar geologic conditions for future acquisition designs.

scholarly journals The GRETA project: the contribution of near-surface geothermal energy for the energetic self-sufficiency of Alpine regions

2017 ◽  
Vol 6 (1) ◽  
Author(s):  
Alessandro Casasso ◽  
Bruno Piga ◽  
Rajandrea Sethi ◽  
Joerg Prestor ◽  
Simona Pestotnik ◽  
...  
Keyword(s):  
Geothermal Energy ◽  
Primary Energy ◽  
Economic Activities ◽  
Geothermal Heat ◽  
Geothermal Resources ◽  
Near Surface ◽  
Alpine Regions ◽  
Heating And Cooling ◽  
Geothermal Heat Pump ◽  
Alpine Space

The Alpine regions are deeply involved in the challenge set by climate change, which is a threat for their environment and for important economic activities such as tourism. The heating and cooling of buildings account for a major share of the total primary energy consumption in Europe, and hence the energy policies should focus on this sector to achieve the greenhouse gas reduction targets set by international agreements. Geothermal heat pump is one of the least carbon-intensive technologies for the heating and cooling of buildings. It exploits the heat stored within the ground, a local renewable energy source which is widely available across the Alpine territory. Nevertheless, it has been little considered by European policies and cooperation projects. GRETA (near-surface Geothermal REsources in the Territory of the Alpine space) is a cooperation project funded by the EU INTERREG-Alpine Space program, aiming at demonstrating the potential of shallow geothermal energy and to foster its integration into energy planning instruments. It started in December 2015 and will last three years, involving 12 partners from Italy, France, Switzerland, Germany, Austria, and Slovenia. In this paper, the project is presented, along with the results of the first year of work.

scholarly journals Finite-difference modelling to evaluate seismic P-wave and shear-wave field data

Solid Earth ◽  
2015 ◽  
Vol 6 (1) ◽  
pp. 33-47 ◽  
Author(s):  
T. Burschil ◽  
T. Beilecke ◽  
C. M. Krawczyk
Keyword(s):  
Wave Field ◽  
Shear Wave ◽  
Field Data ◽  
P Wave ◽  
Sh Wave ◽  
Surface Shear ◽  
Near Surface ◽  
Reflection Seismic ◽  
Surface Shear Wave ◽  
Seismic Measurements

Abstract. High-resolution reflection seismic methods are an established non-destructive tool for engineering tasks. In the near surface, shear-wave reflection seismic measurements usually offer a higher spatial resolution in the same effective signal frequency spectrum than P-wave data, but data quality varies more strongly. To discuss the causes of these differences, we investigated a P-wave and a SH-wave seismic reflection profile measured at the same location on the island of Föhr, Germany and applied seismic reflection processing to the field data as well as finite-difference modelling of the seismic wave field. The simulations calculated were adapted to the acquisition field geometry, comprising 2 m receiver distance (1 m for SH wave) and 4 m shot distance along the 1.5 km long P-wave and 800 m long SH-wave profiles. A Ricker wavelet and the use of absorbing frames were first-order model parameters. The petrophysical parameters to populate the structural models down to 400 m depth were taken from borehole data, VSP (vertical seismic profile) measurements and cross-plot relations. The simulation of the P-wave wave-field was based on interpretation of the P-wave depth section that included a priori information from boreholes and airborne electromagnetics. Velocities for 14 layers in the model were derived from the analysis of five nearby VSPs (vP =1600–2300 m s-1). Synthetic shot data were compared with the field data and seismic sections were created. Major features like direct wave and reflections are imaged. We reproduce the mayor reflectors in the depth section of the field data, e.g. a prominent till layer and several deep reflectors. The SH-wave model was adapted accordingly but only led to minor correlation with the field data and produced a higher signal-to-noise ratio. Therefore, we suggest to consider for future simulations additional features like intrinsic damping, thin layering, or a near-surface weathering layer. These may lead to a better understanding of key parameters determining the data quality of near-surface shear-wave seismic measurements.

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