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.

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.

An optimization of the inverse scattering multiple attenuation method for OBS and VC data

Geophysics ◽  
2002 ◽  
Vol 67 (4) ◽  
pp. 1293-1303 ◽  
Author(s):  
Luc T. Ikelle ◽  
Lasse Amundsen ◽  
Seung Yoo
Keyword(s):  
Free Surface ◽  
Data Storage ◽  
Inverse Scattering ◽  
Water Depth ◽  
Seismic Data ◽  
Computation Time ◽  
Ocean Bottom ◽  
Multiple Attenuation ◽  
Obs Data ◽  
Streamer Data

The inverse scattering multiple attenuation (ISMA) algorithm for ocean‐bottom seismic (OBS) data can be formulated in the form of a series expansion for each of the four components of OBS data. Besides the actual data, which constitute the first term of the series, each of the other terms is computed as a multidimensional convolution of OBS data with streamer data, and aims at removing one specific order of multiples. If the streamer data do not contain free‐surface multiples, we found that the computation of only the second term of the series is needed to predict and remove all orders of multiples, whatever the water depth. As the computation of the various terms of the series is the most expensive part of ISMA, this result can produce significant savings in computation time, even in data storage, as we no longer need to store the various terms of the series. For example, if the streamer data contained free‐surface multiples, OBS seismic data of 6‐s duration, corresponding to a geological model of the subsurface with 250‐m water depth, require the computation of five terms of the series for each of the four components of OBS data. With the new implementation, in which the streamer data do not contain free‐surface multiples, we need the computation of only one term of the series for each component of the OBS data. The saving in CPU time for this particular case is at least fourfold. The estimation of the inverse source signature, which is an essential part of ISMA, also benefits from the reduction of the number of terms needed for the demultiple to two because it becomes a linear inverse problem instead of a nonlinear one. Assuming that the removal of multiple events produces a significant reduction in the energy of the data, the optimization of this problem leads to a stable, noniterative analytic solution. We have also adapted these results to the implementation of ISMA for vertical‐cable (VC) data. This implementation is similar to that for OBS data. The key difference is that the basic model in VC imaging assumes that data consist of receiver ghosts of primaries instead of the primaries themselves. We have used the following property to achieve this goal. The combination of VC data with surface seismic data, which do not contain free‐surface multiples, allows us 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. The difference between these two predictions produces data containing only receiver ghosts of primaries.

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.

An inverse‐scattering series method for attenuating multiples in seismic reflection data

Geophysics ◽  
1997 ◽  
Vol 62 (6) ◽  
pp. 1975-1989 ◽  
Author(s):  
Arthur B. Weglein ◽  
Fernanda Araújo Gasparotto ◽  
Paulo M. Carvalho ◽  
Robert H. Stolt
Keyword(s):  
Free Surface ◽  
Inverse Scattering ◽  
Structural Information ◽  
Added Value ◽  
Ocean Bottom ◽  
Inversion Process ◽  
Seismic Reflection Data ◽  
Multiple Attenuation ◽  
Inverse Scattering Series ◽  
Internal Multiples

We present a multidimensional multiple‐attenuation method that does not require any subsurface information for either surface or internal multiples. To derive these algorithms, we start with a scattering theory description of seismic data. We then introduce and develop several new theoretical concepts concerning the fundamental nature of and the relationship between forward and inverse scattering. These include (1) the idea that the inversion process can be viewed as a series of steps, each with a specific task; (2) the realization that the inverse‐scattering series provides an opportunity for separating out subseries with specific and useful tasks; (3) the recognition that these task‐specific subseries can have different (and more favorable) data requirements, convergence, and stability conditions than does the original complete inverse series; and, most importantly, (4) the development of the first method for physically interpreting the contribution that individual terms (and pieces of terms) in the inverse series make toward these tasks in the inversion process, which realizes the selection of task‐specific subseries. To date, two task‐specific subseries have been identified: a series for eliminating free‐surface multiples and a series for attenuating internal multiples. These series result in distinct algorithms for free‐surface and internal multiples, and neither requires a model of the subsurface reflectors that generate the multiples. The method attenuates multiples while preserving primaries at all offsets; hence, these methods are equally well suited for subsequent poststack structural mapping or prestack amplitude analysis. The method has demonstrated its usefulness and added value for free‐surface multiples when (1) the overburden has significant lateral variation, (2) reflectors are curved or dipping, (3) events are interfering, (4) multiples are difficult to identify, and (5) the geology is complex. The internal‐multiple algorithm has been tested with good results on band‐limited synthetic data; field data tests are planned. This procedure provides an approach for attenuating a significant class of heretofore inaccessible and troublesome multiples. There has been a recent rejuvenation of interest in multiple attenuation technology resulting from current exploration challenges, e.g., in deep water with a variable water bottom or in subsalt plays. These cases are representative of circumstances where 1-D assumptions are often violated and reliable detailed subsurface information is not available typically. The inverse scattering multiple attenuation methods are specifically designed to address these challenging problems. To date it is the only multidimensional multiple attenuation method that does not require 1-D assumptions, moveout differences, or ocean‐bottom or other subsurface velocity or structural information for either free‐surface or internal multiples. These algorithms require knowledge of the source signature and near‐source traces. We describe several current approaches, e.g., energy minimization and trace extrapolation, for satisfying these prerequisites in a stable and reliable manner.

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).

Passive Seismic Marchenko Imaging

2020 ◽  
Author(s):  
Zhongyuan Jin
Keyword(s):  
Free Surface ◽  
Seismic Data ◽  
Low Cost ◽  
Body Waves ◽  
Seismic Survey ◽  
Significant Difference ◽  
Passive Seismic ◽  
Seismic Acquisition ◽  
Imaging Property ◽  
Internal Multiples

<p>In recent years, seismic interferometry (SI) has been widely used in passive seismic data, it allows to retrieve new seismic responses among physical receivers by cross-correlation or multidimensional deconvolution (MDD). Retrieval of reflected body waves from passive seismic data has been proved to be feasible. Marchenko method, as a new technique, retrieves Green’s functions directly inside the medium without any physical receiver there. Marchenko method retrieves precise Green’s functions and the up-going and down-going Green’s functions can be used in target-oriented Marchenko imaging, and internal multiples related artifacts in Marchenko image can be suppressed. </p><p>Conventional Marchenko imaging uses active seismic data, in this abstract, we propose the method of passive seismic Marchenko imaging (PSMI) which retrieves Green’s functions from ambient noise signal. PSMI employs MDD method to obtain the reflection response without free-surface interaction as an input for Marchenko algorithm, such that free-surface multiples in the retrieved shot gathers can be eliminated, besides, internal multiples don’t contribute to final Marchenko image, which means both free-surface multiples and internal multiples have been taken into account. Although the retrieved shot gathers are contaminated by noises, the up-going and down-going Green’s functions can be still retrieved. Results of numerical tests validate PSMI’s feasibility and robustness. PSMI provides a new way to image the subsurface structure, it combines the low-cost property of passive seismic acquisition and target-oriented imaging property of Marchenko imaging, as well as the advantage that there are no artifacts caused by internal multiples and free-surface multiples.</p><p>Overall, the significant difference between PSMI and conventional Marchenko imaging is that passive seismic data is used into Marchenko scheme, which extends the Marchenko imaging to passive seismic field. Passive seismic Marchenko imaging avoids the effects of free-surface multiples and internal multiples in the retrieved shot gathers. PSMI combines the low-cost property of passive seismic acquisition and target-oriented imaging property of Marchenko imaging which is promising in future field seismic survey.</p><p>This work is supported by the Fundamental Research Funds for the Central Universities (JKY201901-03). </p>

Fast free surface multiples attenuation workflow for three-dimensional ocean bottom seismic data

2009 ◽  
Vol 57 (5) ◽  
pp. 785-802 ◽  
Author(s):  
Bärbel Traub ◽  
Anh Kiet Nguyen ◽  
Matthias Riede
Keyword(s):  
Free Surface ◽  
Seismic Data ◽  
Three Dimensional ◽  
Ocean Bottom

A comparison of streamer and OBC seismic data at Beryl Alpha field, U. K. North Sea

Geophysics ◽  
2007 ◽  
Vol 72 (3) ◽  
pp. B69-B80 ◽  
Author(s):  
Jonathan Stewart ◽  
Andrew Shatilo ◽  
Charlie Jing ◽  
Tommie Rape ◽  
Richard Duren ◽  
...  
Keyword(s):  
North Sea ◽  
Seismic Data ◽  
Signal To Noise Ratio ◽  
Vertical Component ◽  
Hard Water ◽  
Detailed Comparison ◽  
P Wave ◽  
Data Sets ◽  
Ocean Bottom ◽  
Streamer Data

Compressional P-wave ocean-bottom-cable (OBC) seismic data from the Beryl Alpha field in the U. K. North Sea provide a superior image of the subsurface compared to heritage streamer seismic data. To determine the reason for the superiority of OBC data, the results of a detailed comparison of these OBC and streamer data sets are compared. The streamer and OBC data sets are reprocessed using a strategy that attempts to isolate the roles of processing, fold, azimuth, PZ combination, and hydrophone and geophone data have on the improved OBC image. The vertical component of the geophone (OBC Z) provides the major contribution to the improved OBC image. The imaged OBC Z datacontain fewer multiples and have a higher signal-to-noise ratio than the streamer. The OBC data have a lower level of multiple contamination because of the contribution from the OBC Z component, together with an effective suppression of receiver-side water-column reverberations as a result of the combination of the OBC hydrophone and geophone traces (PZ combination). The increased fold and wider azimuths of OBC data improve the OBC image slightly. Wider azimuths improve fault imaging, especially for faults oriented obliquely to the inline and crossline directions. The particular conditions at Beryl Alpha field that make the OBC survey successful are the relatively hard water bottom and the presence of multiples that are difficult to remove from streamer data using standard demultiple techniques.

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