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.

  • PGS Marks 25th GeoStreamer 4D

    TechNote - 1 June 2018

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  • Shallow Hazard Imaging (SHAZ)

    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.

  • Improved Reservoir Characterization from Integration of Towed Streamer EM and Dual-sensor Broadband Seismic Data

    12 June 2017

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    We present a data integration study for reservoir characterization, resulting in estimates of hydrocarbon saturation in place within a reservoir. The limitations of using only seismic data for detailed reservoir characterization are well recognized. Seismic data are well suited to resolving structure and some rock properties, notably porosity, but attempts to map fluids from seismic data may be misleading due to the ambiguity between fluid and lithology effects. It is well known that CSEM data are sensitive to the presence of hydrocarbons, but the diffusive energy propagation results in low resolution images. Thus, a careful combination of both types of data helps to overcome their individual weaknesses. In this paper, we outline with a dataset example how the CSEM and seismic data can be integrated together with limited rock physical knowledge in the
    prospect area to estimate the total volume of hydrocarbon in place.

  • A Practical Method for Multi-source Deblending Using Spatio-temporal Compressive Sensing

    12 June 2017

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    This paper presents a new method for simultaneous source deblending developed in the context of compressive sensing. The deblending solution is formulated as an inverse problem which is solved in local overlapping spatiotemporal widows extracted from the blended data. To constrain the solution, the unknown sources are assumed to have a reduced rank with minimal nuclear norm. This will promote the sparsity of seismic data without relying on the use of a given data decomposition method such as a Fourier or curvelet transform. In our case, the
    decomposition is data-driven which arguably would lead to better data modeling and therefore a better source separation. The proposed method is generic and can be applied to all configurations of simultaneous shooting. Test results on triple-source data show a good deblending quality which preserves the frequency content of the data after separation. The proposed method is robust to acquisition noise such as swell allowing it to be flexibly applied at early stages of a typical marine seismic processing sequence.

  • Triassic Regional Rock Physics Study in the Eastern Barents Sea for Prospectivity Analysis

    12 June 2017

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    The first block for exploration in the formerly disputed zone between Norway and Russia (PL589) was awarded in 2016 and is located 250 kilometres from the  earest exploration well. The main objectives of the study were to assess the potential prospectivity of the Late Neogene uplifted Triassic targets using rock physics to take into account the impact of the uplift in an attempt to de-risk observed amplitude versus angle (AVA) seismic anomalies identified on pre-stack broadband seismic data at the Triassic level.
    The significant uplift during the Late Neogene in the Barents Sea area did not allow for a simple regional rock physics model to be established in order to interpret these anomalies. To address this challenge a regional rock physics model based on 13 wells was built taking into account the uplift to model the expected response at the Triassic reservoir level. This study indicates that porosity might be preserved around the PL589 area in the Triassic and helped classify anomalous channelised sandstones using relative acoustic impedance and relative Vp/Vs properties as potentially hydrocarbon filled.

  • The Impact of Wave-Induced Source Variations On 4D Repeatability

    12 June 2017

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    Small waveform and directivity variations of marine airgun signatures due to waves interacting with the source float are a source of 4D noise. We are assessing the magnitude of this noise by first measuring the amount of variability from near-source auxiliary data and then modeling synthetic time-lapse ocean bottom seismic data with realistic source variations based on the measured statistics and standard ocean wave models. We quantify the contribution of source variations to 4D noise as a function of sea state by calculating the NRMSD attribute in the image domain. We find that up to 4% NRMSD can be attributed to source variations under realistic scenarios, with two main contributing effects: variations of individual gun signatures due to pressure changes, and array directivity variations due to the wave-induced pitch and roll of the source floats. The latter effect has a larger impact on the 4D noise in our simulations and depends more on the wave steepness rather than the wave height. While waveform variations can be addressed by a nearfield-based shot-by-shot designature, directivity variations are difficult to correct without knowledge of the sea surface shape.