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.

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.

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.

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.

Designing an exploration-scale OBN: Acquisition design for subsalt imaging and velocity determination

2020 ◽  
Vol 39 (4) ◽  
pp. 248-253
Author(s):  
Joakim Blanch ◽  
Jon Jarvis ◽  
Chris Hurren ◽  
Alex Kostin ◽  
Yan Liu ◽  
...  
Keyword(s):  
Hydrocarbon Exploration ◽  
Direct Wave ◽  
Seismic Surveys ◽  
The Earth ◽  
Seismic Surveying ◽  
Seismic Acquisition ◽  
Physical Limitations ◽  
Marine Seismic ◽  
Subsalt Imaging ◽  
Physical Phenomena

Direct wave arrivals are the most robust signals to determine velocity. They have been used for almost a century in hydrocarbon exploration. This is because the arrival time is explicitly available and provides a direct measurement of the average velocity of the subsurface raypath. To acquire these direct arrivals in a seismic experimental setting, it is necessary that the waves turn back to the surface after they start traveling into the earth. As is well known, it is possible to turn waves back up if they encounter faster propagation velocities than previously experienced. Using these simple concepts, we show how it is possible to design a seismic acquisition to measure subsalt velocities when the salt cover is very thick and potentially not homogeneous. Until now in marine seismic surveying, the physical limitations of the earth meant that the use of direct wave arrivals was restricted to relatively shallow depths of investigation. By combining the application of node technology with a well-established physical phenomena (i.e., refraction in the basement), it is possible to retrieve subsalt velocities from seismic surveys.

scholarly journals Multiple prediction through inversion: Theoretical advancements and real data application

Geophysics ◽  
2007 ◽  
Vol 72 (2) ◽  
pp. V33-V39 ◽  
Author(s):  
Yanghua Wang
Keyword(s):  
Explicit Knowledge ◽  
Real Data ◽  
Second Phase ◽  
Multiple Model ◽  
Subsurface Structures ◽  
Multiple Attenuation ◽  
Data Application ◽  
Multiple Prediction ◽  
Marine Seismic ◽  
Surface Operator

Wave-equation-based multiple attenuation seismic methods may be divided into the two distinct phases of multiple modeling and multiple subtraction. These two are interrelated and must be optimized in order to produce an optimal final result. The multiple prediction through inversion (MPI) scheme updates the multiple model iteratively, as we usually do in a linearized inverse problem. The scheme models the multiple wavefield without an explicit knowledge of surface and subsurface structures or of the source signature; both are generally unknown in seismic surveys. However, compared to a conventional surface-related multiple attenuation method, the accuracy of the multiple model is improved both kinematically and dynamically. It is because the MPI scheme implicitly takes account of the spatial variation of the surface reflectivity, the source signature, the detector patterns and receiver ghosts, and other effects included in the so-called surface operator. When the MPI scheme is used in the first phase it also significantly reduces the nonlinearity of the problem in the second phase that involves attenuating multiples without removing or altering primaries. The effectiveness of the MPI scheme is demonstrated by examples involving real marine seismic data.

scholarly journals A perspective on 3D surface-related multiple elimination

Geophysics ◽  
2010 ◽  
Vol 75 (5) ◽  
pp. 75A245-75A261 ◽  
Author(s):  
Bill Dragoset ◽  
Eric Verschuur ◽  
Ian Moore ◽  
Richard Bisley
Keyword(s):  
Spatial Distribution ◽  
Field Data ◽  
Data Sets ◽  
Data Interpolation ◽  
It Use ◽  
Data Sparseness ◽  
Multiple Attenuation ◽  
3D Surface ◽  
Multiple Prediction ◽  
Multiple Elimination

Surface-related multiple elimination (SRME) is an algorithm that predicts all surface multiples by a convolutional process applied to seismic field data. Only minimal preprocessing is required. Once predicted, the multiples are removed from the data by adaptive subtraction. Unlike other methods of multiple attenuation, SRME does not rely on assumptions or knowledge about the subsurface, nor does it use event properties to discriminate between multiples and primaries. In exchange for this “freedom from the subsurface,” SRME requires knowledge of the acquisition wavelet and a dense spatial distribution of sources and receivers. Although a 2D version of SRME sometimes suffices, most field data sets require 3D SRME for accurate multiple prediction. All implementations of 3D SRME face a serious challenge: The sparse spatial distribution of sources and receivers available in typical seismic field data sets does not conform to the algorithmic requirements. There are several approaches to implementing 3D SRME that address the data sparseness problem. Among those approaches are pre-SRME data interpolation, on-the-fly data interpolation, zero-azimuth SRME, and true-azimuth SRME. Field data examples confirm that (1) multiples predicted using true-azimuth 3D SRME are more accurate than those using zero-azimuth 3D SRME and (2) on-the-fly interpolation produces excellent results.

scholarly journals PENERAPAN METODE F-K DEMULTIPLE DALAM KASUS ATENUASI WATER-BOTTOM MULTIPLE

2016 ◽  
Vol 11 (1) ◽  
pp. 33
Author(s):  
Subarsyah Subarsyah ◽  
Sahudin Sahudin
Keyword(s):  
Seismic Data ◽  
Final Section ◽  
Signal To Noise Ratio ◽  
Multiple Reflections ◽  
Seismic Section ◽  
Multiple Attenuation ◽  
Seismic Acquisition ◽  
Marine Seismic ◽  
Second Category ◽  
Water Bottom

Keberadaan water-bottom multiple merupakan hal yang tidak bisa dihindari dalam akuisisi data seismik laut, tentu saja hal ini akan menurunkan tingkat perbandingan sinyal dan noise. Beberapa metode atenuasi telah dikembangkan dalam menekan noise ini. Metode atenuasi multiple diklasifikasikan dalam tiga kelompok meliputi metode dekonvolusi yang mengidentifikasi multiple berdasarkan periodisitasnya, metode filtering yang memisahkan refleksi primer dan multiple dalam domain tertentu (F-K,Tau-P dan Radon domain) serta metode prediksi medan gelombang. Penerapan metode F-K demultiple yang masuk kategori kedua akan diterapkan terhadap data seismik PPPGL tahun 2010 di perairan Teluk Tomini. Atenuasi terhadap water-bottom multiple berhasil dilakukan akan tetapi pada beberapa bagian multiple masih terlihat dengan amplitude relatif lebih kecil. F-K demultiple tidak efektif dalam mereduksi multiple pada offset yang pendek dan multiple pada zona ini yang memberikan kontribusi terhadap keberadaan multiple pada penampang akhir. Kata kunci : F-K demultiple, multiple, atenuasi The presence of water-bottom multiple is unavoidable in marine seismic acquisition, of course, this will reduce signal to noise ratio. Several attenuation methods have been developed to suppress this noise. Multiple attenuation methods are classified into three groups first deconvolution method based on periodicity, second filtering method that separates the primary and multiple reflections in certain domains (FK, Tau-P and the Radon domain) ang the third method based on wavefield prediction. Application of F-K demultiple incoming second category will be applied to the seismic data in 2010 PPPGL at Tomini Gulf waters. Attenuation of the water-bottom multiple successful in reduce multiple but in some parts of seismic section multiple still visible with relatively smaller amplitude. FK demultiple not effective in reducing multiple at near offset and multiple in this zone contribute to the existence of multiple in final section. Key words : F-K demultiple, multiple, attenuation

Revitalizing Seismic Beyond Geometry Limitations: A Case Study of OBN Survey in Offshore Sabah

2021 ◽  
Author(s):  
Lee Sii Ngo ◽  
Wai Leng Cheah ◽  
Artem Sazykin ◽  
Gavin Menzel-Jones ◽  
Joyce Li Wong ◽  
...  
Keyword(s):  
Model Building ◽  
Waveform Inversion ◽  
Water Environment ◽  
Low Frequency ◽  
Earth Model ◽  
Ocean Bottom ◽  
Full Waveform ◽  
Seismic Acquisition ◽  
Marine Seismic

Abstract Ocean-bottom node (OBN) surveys are an increasingly common choice of method for marine seismic acquisition and offer several key advantages. These include recording wide-azimuth data and reliable low-frequency information. Since the start of OBN acquisition almost two decades ago, key challenges remain, not only on equipment handling and data management, but also on the data processing and imaging methodologies as these multicomponent workflows continue to evolve. We present a case study of an OBN survey acquired in offshore Sabah with a cross-spread geometry, in an ultra-shallow-water environment. This study discusses a few key processing challenges encountered due to this sparse acquisition including noise and multiple energy contamination and aliasing on data. We explain the challenges, how these were overcome, and the methodologies we used to enhance the data quality. As the main product for this project is a depth-imaged seismic volume, we also describe the earth model building workflow and imaging tools we used to leverage the advantage of full-azimuth data and multidirectional wavefield recorded in this survey. This includes full-waveform inversion, multi-azimuth tomography, and imaging with multiple.

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.

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