Elimination of free‐surface related multiples without need of the source wavelet

Geophysics ◽  
2001 ◽  
Vol 66 (1) ◽  
pp. 327-341 ◽  
Author(s):  
Lasse Amundsen
Keyword(s):  
Free Surface ◽  
Vertical Component ◽  
Ocean Bottom ◽  
Pressure Derivative ◽  
Direct Wave ◽  
Marine Source ◽  
Marine Seismic ◽  
Multiple Elimination ◽  
Data Frequency ◽  
Source Array

This paper presents a new, wave‐equation based method for eliminating the effect of the free surface from marine seismic data without destroying primary amplitudes and without any knowledge of the subsurface. Compared with previously published methods which require an estimate of the source wavelet, the present method has the following characteristics: it does not require any information about the marine source array and its signature, it does not rely on removal of the direct wave from the data, and it does not require any explicit deghosting. Moreover, the effect of the source signature is removed from the data in the multiple elimination process by deterministic signature deconvolution, replacing the original source signature radiated from the marine source array with any desired wavelet (within the data frequency‐band) radiated from a monopole point source. The fundamental constraint of the new method is that the vertical derivative of the pressure or the vertical component of the particle velocity is input to the free‐surface demultiple process along with pressure recordings. These additional data are routinely recorded in ocean‐bottom seismic surveys. The method can be applied to conventional towed streamer pressure data recorded in the water column at a depth which is greater than the depth of the source array only when the pressure derivative can be estimated, or even better, is measured. Since the direct wave and its source ghost is part of the free‐ surface demultiple, designature process, the direct arrival must be properly measured for the method to work successfully. In the case when the geology is close to horizontally layering, the free‐surface multiple elimination method greatly simplifies, reducing to a well‐known deterministic deconvolution process which can be applied to common shot gathers (or common receiver gathers or common midpoint gathers when source array variations are negligible) in the τ-p domain or frequency‐wavenumber domain.

scholarly journals A review of OBN processing: challenges and solutions

2021 ◽  
Vol 18 (4) ◽  
pp. 492-502
Author(s):  
Dongliang Zhang ◽  
Constantinos Tsingas ◽  
Ahmed A Ghamdi ◽  
Mingzhong Huang ◽  
Woodon Jeong ◽  
...  
Keyword(s):  
Significant Shift ◽  
Ocean Bottom ◽  
Direct Wave ◽  
Multiple Attenuation ◽  
Wavefield Separation ◽  
Seismic Acquisition ◽  
Cascaded Model ◽  
Multiple Prediction ◽  
Marine Seismic ◽  
Multiple Elimination

Abstract In the last decade, a significant shift in the marine seismic acquisition business has been made where ocean bottom nodes gained a substantial market share from streamer cable configurations. Ocean bottom node acquisition (OBN) can acquire wide azimuth seismic data over geographical areas with challenging deep and shallow bathymetries and complex subsurface regimes. When the water bottom is rugose and has significant elevation differences, OBN data processing faces a number of challenges, such as denoising of the vertical geophone, accurate wavefield separation, redatuming the sparse receiver nodes from ocean bottom to sea level and multiple attenuation. In this work, we review a number of challenges using real OBN data illustrations. We demonstrate corresponding solutions using processing workflows comprising denoising the vertical geophones by using all four recorded nodal components, cross-ghosting the data or using direct wave to design calibration filters for up- and down-going wavefield separation, performing one-dimensional reversible redatuming for stacking QC and multiple prediction, and designing cascaded model and data-driven multiple elimination applications. The optimum combination of the mentioned technologies produced cleaner and high-resolution migration images mitigating the risk of false interpretations.

Attenuation of free-surface multiples by up/down deconvolution for marine towed-streamer data

Geophysics ◽  
2011 ◽  
Vol 76 (6) ◽  
pp. V129-V138 ◽  
Author(s):  
Mariusz Majdański ◽  
Clément Kostov ◽  
Ed Kragh ◽  
Ian Moore ◽  
Mark Thompson ◽  
...  
Keyword(s):  
Free Surface ◽  
Field Data ◽  
Near Field ◽  
Synthetic Data ◽  
Ocean Bottom ◽  
The North ◽  
The North Sea ◽  
Marine Seismic ◽  
Streamer Data ◽  
Multiple Elimination

Free-surface-related multiples in marine seismic data are commonly attenuated using adaptive subtraction of the predicted multiple energy. An alternative method, based on deconvolution of the upgoing wavefield by the downgoing wavefield, was previously applied to ocean-bottom data. We apply the deconvolution method to towed-streamer data acquired in an over/under configuration. We also use direct arrival deconvolution that results in source wavelet designature only, as a benchmark to verify the full multiple deconvolution result. Detailed synthetic data analysis, including sensitivity tests, explains each data processing step and its effects on the final result. We then apply this verified preprocessing sequence to field data from the Kristin area of the North Sea, with a focus on the direct arrival prediction using the near-field hydrophone method. Prestack evaluation of the results shows that the method applied to the field data provides designature, source-side deghosting, and attenuation of multiples. We show comparable stacked results from our method and from 2D iterative surface-related multiple elimination. The workflow has the benefit that it does not require an adaptive subtraction step or iterative application. However, an accurate direct arrival prediction is essential for the successful application of the method. This prediction is obtained using near-field hydrophone measurements that can be recorded with some commercial acquisition systems.

Preliminary interpretation of a marine deep seismic sounding survey in the region of Explorer ridge

1976 ◽  
Vol 13 (11) ◽  
pp. 1545-1555 ◽  
Author(s):  
R. M. Clowes ◽  
S. J. Malecek
Keyword(s):  
Upper Mantle ◽  
Vertical Component ◽  
Thick Layer ◽  
Deep Seismic Sounding ◽  
Ocean Bottom ◽  
Reflected Waves ◽  
Juan De Fuca Plate ◽  
Seismic Sounding ◽  
First Arrival ◽  
Marine Seismic

A marine seismic system for recording near-vertical incidence to wide-angle reflected waves and refracted waves with penetration from the ocean bottom to the upper mantle (deep seismic sounding or DSS) has been developed. Signals from six individual hydrophones suspended at 45 m depth from a 600 m cable trailed behind the receiving ship are recorded in digital form. Using charges ranging from 2.3 to 280 kg, two reversed DSS profiles were recorded in the region of Explorer ridge during 1974. A preliminary interpretation of the profiles based on first-arrival information in the range 4 to 80 km has been made.The reversed profile run across the ridge showed no anomalous effects as the ridge was crossed; the profile on Juan de Fuca plate, paralleling the ridge, exhibited traveltime branch offsets and delays. These have been interpreted as due to faulting with a vertical component of offset of about 4 km. The reversed upper mantle velocities are 7.85 and'7.30 km/s indirections perpendicular and parallel to the ridge. Anisotropy is proposed to explain these different velocities and gives a 7% anisotropic effect. The data require that 'layer 2' comprise at least two layers with velocities of 4.13 km/s and 5.25 km/s and individual depth extents ranging from 1 to 2 km. Compared with crustal sections from other ridge areas, the interpretation gives a thick 'layer 3' (up to 6 km) near the ridge crest. The sub-bottom thickness of the oceanic crust varies between 7 and 9 km, except in the faulted region, where the 7.30 km/s material is present less than 3 km from the bottom.

Using even terms of the scattering series for deghosting and multiple attenuation of ocean‐bottom cable data

Geophysics ◽  
1999 ◽  
Vol 64 (2) ◽  
pp. 579-592 ◽  
Author(s):  
Luc T. Ikelle
Keyword(s):  
Free Surface ◽  
Seismic Data ◽  
Primary Energy ◽  
Ocean Bottom ◽  
Receiver Side ◽  
Direct Wave ◽  
Sea Floor ◽  
Multiple Attenuation ◽  
Marine Surface ◽  
Streamer Data

Inverse scattering multiple attenuation (ISMA) is a method of removing free‐surface multiple energy while preserving primary energy. The other key feature of ISMA is that no knowledge of the subsurface is required in its application. I have adapted this method to multicomponent ocean‐bottom cable data (i.e., to arrays of sea‐floor geophones and hydrophones) by selecting a subseries made of even terms of the current scattering series used in the free‐surface multiple attenuation of conventional marine surface seismic data (streamer data). This subseries approach allows me to remove receiver ghosts (receiver‐side reverberations) and free‐surface multiples (source‐side reverberations) in multicomponent OBC data. I have processed each component separately. As for the streamer case, my OBC version of ISMA preserves primary energy and does not require any knowledge of the subsurface. Moreover, the preprocessing steps of muting for the direct wave and interpolating for missing near offsets are no longer needed. Knowledge of the source signature is still required. The existing ways of satisfying this requirement for streamer data can be used for OBC data without modification. This method differs from the present dual‐field deghosting method used in OBC data processing in that it does not assume a horizontally flat sea floor; nor does it require the knowledge of the acoustic impedance below the sea floor. Furthermore, it attenuates all free‐surface multiples, including receiver ghosts and source‐side reverberations.

Attenuating primaries and free‐surface multiples of vertical cable (VC) data while preserving receiver ghosts of primaries

Geophysics ◽  
2001 ◽  
Vol 66 (3) ◽  
pp. 953-963 ◽  
Author(s):  
Luc T. Ikelle
Keyword(s):  
Free Surface ◽  
Seismic Data ◽  
Ocean Bottom ◽  
Direct Wave ◽  
Sea Floor ◽  
Multiple Attenuation ◽  
Wavefield Separation ◽  
Internal Multiples ◽  
Streamer Data ◽  
Imaging Algorithms

Marine vertical cable (VC) data contain primaries, receiver ghosts, free‐surface multiples, and internal multiples just like towed‐streamer data. However, the imaging of towed‐streamer data is based on primary reflections, while the emerging imaging algorithms of VC data tend to use the receiver ghosts of primary reflections instead of the primaries themselves. I present an algorithm for attenuating primaries, free‐surface multiples, and the receiver ghosts of free‐surface multiples while preserving the receiver ghosts of primaries. My multiple attenuation algorithm of VC data is based on an inverse scattering approach known, which is a predict‐then‐subtract method. It assumes that surface seismic data are available or that they can be computed from VC data after an up/down wavefield separation at the receiver locations (streamer data add to VC data some of the wave paths needed for multiple attenuation). The combination of surface seismic data with VC data allows one to predict free‐surface multiples and receiver ghosts as well as the receiver ghosts of primary reflections. However, if the direct wave arrivals are removed from the VC data, this combination will not predict the receiver ghosts of primary reflections. I use this property to attenuate primaries, free‐surface multiples, and receiver ghosts from VC data, preserving only the receiver ghosts of primaries. This method can be used for multicomponent ocean bottom cable data (i.e., arrays of sea‐floor geophones and hydrophones) without any modification to attenuate primaries, free‐surface multiples, and the receiver ghosts of free‐surface multiples while preserving the receiver ghosts of primaries.

Multiple water reflections recorded at the ocean bottom

1978 ◽  
Vol 15 (1) ◽  
pp. 78-85 ◽  
Author(s):  
George A. McMechan
Keyword(s):  
Vertical Component ◽  
Standard Technique ◽  
Ocean Bottom ◽  
Seismic Profiles ◽  
Multiple Reflections ◽  
Air Water Interface ◽  
Time Distance ◽  
Marine Seismic ◽  
Ray Parameter ◽  
Sediment Interface

The use of direct arrivals and multiple reflections that have travelled completely in water from source to receiver to determine epicentral distances is a standard technique in the analysis of marine seismic profiles. The configuration of a source at the air–water interface and a seismometer at the water–sediment interface is investigated in the ray parameter – distance plane and the travel time – distance plane. Vertical component synthetic seismograms are computed by the Cagniard – de Hoop algorithm and are compared with seismograms recorded at the ocean bottom. The results explain the prominent features of the observed wavetrains, including the asymptotic behaviour of arrivals, the location of caustics and the variable observability of arrivals as a fu nction of distance.

Multidimensional signature deconvolution and free‐surface multiple elimination of marine multicomponent ocean‐bottom seismic data

Geophysics ◽  
2001 ◽  
Vol 66 (5) ◽  
pp. 1594-1604 ◽  
Author(s):  
Lasse Amundsen ◽  
Luc T. Ikelle ◽  
Lars E. Berg
Keyword(s):  
Free Surface ◽  
Seismic Data ◽  
Local Density ◽  
Normal Component ◽  
Time Derivative ◽  
Ocean Bottom ◽  
Sea Floor ◽  
Reflection Data ◽  
Scattered Fields ◽  
Source Array

This paper presents a wave‐equation method for multidimensional signature deconvolution (designature) and elimination of free‐surface related multiples (demultiple) in four‐component (4C) ocean‐bottom seismic data. The designature/demultiple method has the following characteristics: it preserves primary amplitudes while attenuating free‐surface related multiples; it requires no knowledge of the sea floor‐parameters and the subsurface; it requires information only of the local density and acoustic wave propagation velocity just above the sea floor; it accommodates source arrays; and no information (except location) of the physical source array, its volume, and its radiation characteristics (wavelet) is required. Designature is an implicit part of the demultiple process; hence, the method is capable of transforming recorded reflection data excited by any source array below the sea surface into free‐surface demultipled data that would be recorded from a point source with any desired signature. In addition, the incident wavefield is not subtracted from the data prior to free‐surface demultiple; hence, separation of incident and scattered fields is not an issue as it is for most other free‐surface demultiple schemes. The designature/demultiple algorithm can be divided into two major computational steps. First, a multidimensional deconvolution operator, inversely proportional to the time derivative of the downgoing part of the normal component of the particle velocity just above the sea floor, is computed. Second, an integral equation is solved to find any component of the designatured, free‐surface demultipled multicomponent field. When the geology is horizontally layered, the designature and free‐surface demultiple scheme greatly simplifies and lends itself toward implementation in the τ‐p domain or frequency‐wavenumber domain as deterministic deconvolution of common shot gathers (or common receiver gathers when source array variations are negligible).

LONG-PERIOD SURFACE-RELATED MULTIPLE SUPPRESSION IN 2D MARINE SEISMIC DATA USING PREDICTIVE DECONVOLUTION AND COMBINATION OF SURFACE-RELATED MULTIPLE ELIMINATION AND PARABOLIC RADON FILTERING

2021 ◽  
Author(s):  
Pimpawee Sittipan ◽  
Pisanu Wongpornchai
Keyword(s):  
Seismic Data ◽  
Seismic Reflection ◽  
Petroleum Reservoirs ◽  
The United States ◽  
Multiple Reflections ◽  
Long Period ◽  
Predictive Deconvolution ◽  
Short Period ◽  
Marine Seismic ◽  
Multiple Elimination

Some of the important petroleum reservoirs accumulate beneath the seas and oceans. Marine seismic reflection method is the most efficient method and is widely used in the petroleum industry to map and interpret the potential of petroleum reservoirs. Multiple reflections are a particular problem in marine seismic reflection investigation, as they often obscure the target reflectors in seismic profiles. Multiple reflections can be categorized by considering the shallowest interface on which the bounces take place into two types: internal multiples and surface-related multiples. Besides, the multiples can be categorized on the interfaces where the bounces take place, a difference between long-period and short-period multiples can be considered. The long-period surface-related multiples on 2D marine seismic data of the East Coast of the United States-Southern Atlantic Margin were focused on this research. The seismic profile demonstrates the effectiveness of the results from predictive deconvolution and the combination of surface-related multiple eliminations (SRME) and parabolic Radon filtering. First, predictive deconvolution applied on conventional processing is the method of multiple suppression. The other, SRME is a model-based and data-driven surface-related multiple elimination method which does not need any assumptions. And the last, parabolic Radon filtering is a moveout-based method for residual multiple reflections based on velocity discrimination between primary and multiple reflections, thus velocity model and normal-moveout correction are required for this method. The predictive deconvolution is ineffective for long-period surface-related multiple removals. However, the combination of SRME and parabolic Radon filtering can attenuate almost long-period surface-related multiple reflections and provide a high-quality seismic images of marine seismic data.

Enhancing Signal-to-Noise Ratios of High-Frequency Rayleigh Waves Extracted from Ambient Seismic Noises in Topographic Region

2020 ◽  
Vol 110 (2) ◽  
pp. 793-802
Author(s):  
Ping Ping ◽  
Risheng Chu ◽  
Yu Zhang ◽  
Jun Xie
Keyword(s):  
Free Surface ◽  
Correlation Functions ◽  
High Frequency ◽  
Rayleigh Waves ◽  
Vertical Component ◽  
Noise Correlation ◽  
Surface Boundary ◽  
Elastic Wedge ◽  
Signal To Noise ◽  
Surface Boundary Conditions

ABSTRACT High-frequency Rayleigh waves can be extracted from ambient seismic noises through noise correlation functions (NCFs), which provides a useful tool to image shallow structures in topographic regions, for example, landslides. Topography may affect signal-to-noise ratios (SNRs) of extracted Rayleigh waves. It is necessary to investigate the propagation features of Rayleigh waves passing a 3D topography. Based on the incident and scattered waves satisfying the free surface boundary conditions, we first derive the displacement responses of Rayleigh waves across a 3D elastic wedge. The results show that the particle motions of Rayleigh waves are an ellipse whose longer axis is always perpendicular to the topographic free surface. Therefore, the Qg component, perpendicular to the topographic free surface, is a better choice to extract high-frequency Rayleigh waves than the conventional vertical component. To verify the choice, we carry out numerical simulations to extract high-frequency NCFs for a typical 3D massif model. Finally, we apply this approach to extract high-frequency Rayleigh-wave NCFs on the Xishancun landslide in southwestern China. The NCFs obtained using the Qg component have more coherent waveforms and higher SNRs than those using the vertical component. We conclude that the Qg component has advantages in extracting high-frequency Rayleigh waves over the conventional vertical component.

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