Technical Library

  • Marine Vibrator: Source Wavefield Modeling

    Author: Sander Losnedahl, Okwudili Orji, Walter Söllner
    SEG - 15 September 2019

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    Traditional marine seismic sources are facing increasingly strict regulation due to their non-negligible environmental foot print. However, marine vibrators are easy to control, are
    more efficient and have lower environmental foot print. Here we demonstrate source wavefield modeling for marine vibrators, discuss the source signature requirements and
    important processing and imaging steps.

  • Marine vibrator source: Modular projector system

    Author: Okwudili Orji, Mattias Oscarsson, Walter Söllner, ØysteinTrætten
    SEG - 15 September 2019

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    There is a desire by the marine geophysical industry for a seismic source with a low environmental footprint. Received sound pressure level (SPL) and sound exposure level (SEL) can restrict how seismic surveys can be conducted in sensitive areas.
    To address this desire, we have developed a broadband nonimpulsive source based on the concept of modular transducer elements. The source has a controlled output that can emit
    arbitrary signals, enables flexible source geometries, and can produce ultra-low frequency content that facilitates robust full waveform inversion.
    Sea trials and testing indicate that the developed source will meet the challenging output demands and exhibit the necessary robustness to be a viable seismic source for the
    future. Large scale testing is planned in 2019.

  • Least-squares migration with gathers

    Author: Alejandro Valenciano, Mikhail Orlovich, Elena Klochikhina, Nizar Chemingui
    SEG - 15 September 2019

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    Least-Squares Migration (LSM) reduces the amplitude variations due to uneven illumination and migration operator restrictions. When posed as an inversion in the
    angle domain, LSM compensates the angle gather amplitudes and improves their resolution. Our LSM angle extension requires an explicit computation of the Hessian
    matrix or Point Spread Functions (PSFs). The algorithm applies a chain of operators and their adjoints for modeling, migration, and offset to angle transformation to a grid of point scatterers distributed through the model. It effectively incorporates the spatial and angle variability of the PSF.
    The angular reflectivity is recovered by solving a linear system of equations that deconvolves the multidimensional PSF from the migrated image gathers. Results from the
    Sigsbee model and a multisensor streamer survey acquired in the Central North Sea show how LSM improves the image resolution and Amplitude Versus Angle (AVA) reliability.

  • A 3D methodology for residual and diffracted multiple attenuation

    Author: Maiza Bekara, Lian Duan, Mamdouh Salem
    SEG - 15 September 2019

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    Demultiple techniques such as 3D SRME and 3D wave equation modelling are able to model complex surface related multiples to a good extent, particularly in terms of their kinematics. However, the high frequency contents in the multiples model are often lacking due to stacking and/or convolutional operations. In addition, out-of-plane
    diffracted multiples are usually inadequately modelled by these techniques due to coarse streamer sampling. All these factors contribute in lowering the quality of any multiples model. Hence the demultiple process is not sufficient and some residual multiples are left in the data. These multiples would require further attenuation by a post demultiple process.
    This abstract proposes a novel post demultiple solution to attenuate both residual and diffracted multiples. The solution incorporates three main physical attributes that can be used to discriminate between primaries and residual multiples in moderate to deep water surveys: (i) amplitude range, (ii) frequency content and (iii) dip content. The proposed solution can be seen as a 3D frequency and dip dependent de-spiking process with Fourier based reconstruction to preserve primary signal.

  • Amplitude enhancement of RTM angle gathers with deconvolution

    Author: Sean Crawley, Faqi Liu, Elena Klochikhina, Nizar Chemingui, Dan Whitmore
    SEG - 15 September 2019

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    Deconvolution has been routinely applied in seismic processing to enhance the resolution of migrated images. While full multi-dimensional deconvolution is only achievable through computationally expensive least-squares migration, we demonstrate that, when properly implemented, the deconvolution imaging condition can efficiently improve the image resolution and produce more balanced angle gathers. Using both synthetic and a field data examples, we demonstrate the enhancement in the amplitude of the migrated images and angle gathers using a deconvolution imaging condition.

  • How to combine single hydrophone streamers with multi-component streamers in a 4D context: An offshore West Africa case study

    Author: Didier Lecerf. Andrew Oates, Rebekah Brown, Elena Polyaeva, Francois Portaluri, Cyrille Reiser, David Raistrick, Adam Betteridge, Jyoti Kumar
    SEG - 15 September 2019

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    In this paper, we demonstrate how conventional singlehydrophone streamer data can be combined with dualsensor acquisition data to support the reservoir monitoring of a producing field in offshore West Africa. We describe innovative processing techniques for increasing the 4D resolution, and use case study examples to illustrate the methodology. The chosen processing approach intends to extend the signal bandwidth in a 3D and 4D sense.

    Improving the resolution of the 4D signal is essential for understanding the production of this complex reservoir, which is composed of turbiditic stacked channels.

  • Results from a 3D field trial with a seismic acquisition and processing method based on continuous wavefields

    Author: Tilman Klüver, Stian Hegna, and Jostein Lima
    SEG - 15 September 2019

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    This paper describes the acquisition setup and results from a field trial conducted with a novel marine seismic acquisition and processing methodology that utilizes continuous
    wavefields. Compared to a conventional survey previously acquired in the same location, both the peak sound pressure and sound exposure levels were reduced significantly. The
    lateral sampling was improved and trace density increased without loss of acquisition efficiency. The imaging results of the field trial data show deep penetration equivalent to the conventional data despite the significantly lowered source output.

  • Compensating for visco-acoustic affects with an integrated model building flow: a deep water Equatorial Conjugate Margin case study

    Author: Tony Martin, Gareth Venfield, Vikash Chavda
    SEG - 15 September 2019

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    Cretaceous prospects in deep water Côte d’Ivoire data are impacted by later channel and canyon systems. The structural uncertainty and amplitude fidelity of the plays can be affected if unresolved shallow velocity and attenuation issues are not accommodated in the earth model. Using an integrated visco-acoustic model building flow we solve the impact of complex channel systems on deeper targets. Full Waveform Inversion (FWI) created an accurate and regional scale velocity model, removing the structural uncertainty when used in the imaging step. Tomography was used to compensate for visco-acoustic effects. Integrated into the sequence, the method calculated measures of log spectral ratio in demigrated space, mitigating stretch and tuning effects. The amalgamation of the complete visco-acoustic flow accommodated the structural complexity of the area, whilst improving the amplitude reliability of the dataset.

  • Marine vibrator source: Modular projector system

    Author: Okwudili Orji, Mattias Oscarsson, Walter Söllner
    SEG - 15 September 2019

    View summary

    There is a desire by the marine geophysical industry for a seismic source with a low environmental footprint. Received sound pressure level (SPL) and sound exposure level (SEL) can restrict how seismic surveys can be conducted in sensitive areas.
    To address this desire, we have developed a broadband nonimpulsive source based on the concept of modular transducer elements. The source has a controlled output that can emit
    arbitrary signals, enables flexible source geometries, and can produce ultra-low frequency content that facilitates robust full waveform inversion.
    Sea trials and testing indicate that the developed source will meet the challenging output demands and exhibit the necessary robustness to be a viable seismic source for the
    future. Large scale testing is planned in 2019.

  • Enhanced Presalt Imaging Using Iterative Least-Squares Migration: A Case Study in Santos Basin, Brazil

    Author: Sriram Arasanipalai, Hermann Lebit, Pascal Ollagnon, Bruno Virlouvet, Jeff Tilton
    SEG - 15 September 2019

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    Imaging technologies such as Kirchhoff Migration and Reverse Time Migration (RTM) provide a level of seismic resolution that suit the industry’s expectation of capturing
    hydrocarbon reservoirs and outlining prospects. Over the last few years, Least-Squares Migration (LSM) has become the new standard in high-end seismic imaging, providing a
    higher level of granularity necessary for prospect risk mitigation, reservoir characterization and well planning. In this case study, we present the advantages of using an iterative LSM for imaging and interpretation of presalt reservoirs of the Buzios Field in Santos Basin, offshore Brazil.