Whitepapers

  • PGS Brings rockAVO to Africa

    Author: PGS
    TechNote - 4 November 2019

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    The integration of seismic with well data enables oil and gas companies to calibrate PGS GeoStreamer and other seismic data with conditioned well data and known production scenarios.

  • Shallow Hazard Imaging (SHAZ)

    TechNote - 1 June 2018

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  • PGS Marks 25th GeoStreamer 4D

    TechNote - 1 June 2018

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  • Towed Streamer EM - Survey Design and Acquisition

    TechNote - 4 July 2017

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    Towed Streamer EM delivers high density 3D CSEM data with exceptional acquisition
    efficiency. Daily acquisition rates in the order of 140 sq. km are frequently achieved with the current record at over 200 sq. km in a single day. PGS acquires 2D GeoStreamer® data simultaneously with EM data, or 3D EM data over existing or planned 3D seismic.

  • Towed Streamer EM - Feasibility Studies

    TechNote - 4 July 2017

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    PGS conducts EM feasibility studies in order to confirm that the Towed Streamer EM system will be sensitive to changes in target resistivity. A typical feasibility study involves forward modeling for a range of water depths, target depths, target sizes and resistivity scenarios. A feasibility study is not a pre-requisite to EM acquisition; rather it is a useful first step when looking at new areas or play types.

  • Towed Streamer EM - Processing and Inversion

    TechNote - 4 July 2017

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    Towed Streamer EM data is monitored on board the vessel in real time as it is acquired. Once a sail line is complete offline QC is conducted, including a 1D QC inversion of every shot acquired. The EM field deliverable is denoised, navigation merged data, and this is delivered to both the customer and PGS’ EM imaging team for 2.5D and 3D anisotropic inversion which is performed onshore.

  • Seismic Noise Attenuation Using Curvelet Transform and Dip Map Data Structure

    12 June 2017

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    The curvelet transform is a known tool used in the attenuation of coherent and incoherent noise in seismic data. It utilizes the fact that signal and noise are usually better separated in the curvelet domain than in the time-space (TX) domain. Coefficients of the transform are not independent and neighboring coefficients are strongly correlated, which existing curvelet-based noise attenuation algorithms do not fully utilize. In this work, we propose to use a data structure called a ‘dip map’ to describe dip information in seismic data. This information links local curvelet coefficients together in adaptive thresholding or subtraction of curvelet coefficients in seismic denoising algorithms. We used the dip map to improve the curvelet multiple subtraction algorithm and the results show significant improvement over traditional methods with real data.

  • A New Look at the Geology and Prospectivity of a North Sea Frontier Area with Modern Seismic - The East Shetland Platform

    12 June 2017

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    The greater East Shetland Platform (ESP) area is characterized by numerous proven Devonian-Eocene fields, but is still one of the few remaining underexplored regions of the UK Continental Shelf. In particular, Permo-Carboniferous carbonates and sandstones, Devonian sandstones and fractured basement in prominent structural traps have been successful, proving these units to be viable reservoirs. Some of these are large producing fields in nearby areas (e.g., Buchan, Clair, Auk, with >100 MMboe).
    The improved imaging of the 3D broadband dual-sensor towed streamer data has allowed the interpretation of the Paleozoic horizons over the entire outer ESP region (17,500 km2), enabling interpreters to spread new light on its evolution.
    Possible Paleozoic structural traps are often sealed by the overlying Cretaceous strata. Source rocks could be provided by the ‘classical’ upper Jurassic Kimmeridge Clay (lateral migration from the basin depocenters lying further east). Potential additional oil-prone sources may be provided by middle Devonian shales (c.f., Beatrice Field).
    Burial history modelling indicates that the best case scenario (late generation) did occur over parts of the study area. This supports previous geochemical analyses in analogue areas, which suggested a contribution from the Devonian source for the oils of large fields (e.g., Claymore and Clair fields).

  • Intelligent Adaptive Subtraction for Multiple Attenuation

    12 June 2017

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    A lot of improvements have been seen in the last decade in 3D multiple modelling techniques, such as 3D Surface Related Multiple Elimination (SRME) and 3D wavefield modelling. These processes create accurate multiple models in terms of kinematics and amplitude. The main challenge now is to improve the subtraction of multiples, with a reduction in both residual multiple and primary leakage. This paper describes a new approach for multiple adaptive subtraction, which combines different techniques (least squares filtering in the time-space domain and
    curvelet-based subtraction) and improves primary preservation by using true multiple adaptive subtraction. The ultimate aim is to automatically get the best subtraction according to the complexity of the geology with minimum testing for the geophysicist.

  • Shot by Shot Source Wave Field Estimation

    12 June 2017

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    In this paper we discuss the behavior of air gun source arrays in marine seismic acquisition. We comment the fact that the source configuration and depth are changing continually with the combined actions of surface waves, sea currents and general towing conditions. This has a direct effect on the emitted source pressure wave field and thus on the signature in the seismic data. We describe the method of backpropagation with relative motion that allows an efficient and robust estimation of notional and far-field signatures from near-field measurements at every shot point. The derived shot by shot signatures show very good correlation with seastate and sea-currents, as we would expect. We show that the variation of the signature can affect the quality of seismic data. We demonstrate that the estimated far-field signatures describe the real variation of the signature in the data and we show how the estimated shot by shot signatures can be used to mitigate the effect of signature variations and thereby improve the quality of the seismic data.