Technical Library

  • Improved HSEQ and survey efficiency demonstrated with a new remotely operated streamer cleaning tool

    Author: Andrew Long, Rune Tønnessen, Trygve Skadberg, James Wright
    AEGC - 2 September 2019

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    Barnacle growth on seismic streamers creates noise on the recorded signals. Keeping a low noise level in barnacle areas is challenging to seismic crews: Frequent workboat trips are required for streamer cleaning, and workboat operations are weather-dependent and considered undesirable from an HSE perspective. In 2007 a purely mechanical and autonomous streamer cleaning unit (SCU) was introduced that is launched and recovered from the workboat. In 2016 we subsequently developed a
    remotely operated streamer tool (ROST) that is capable of launching and recovering SCUs to/from the streamer without the use of a workboat, and which is therefore less
    affected by weather. The ROST is operated from a support vessel that is independent of the seismic vessel. We present experiences from four surveys that were
    subject to different operating conditions. Operation in high sea states is demonstrated on a survey offshore Namibia, and operation in extreme currents is demonstrated on another survey east of South Africa. A noise removal method is also presented that allows operation of the ROST while online during seismic recording. The method was first applied on the offshore South African survey, and later on two surveys in offshore Angola. It is demonstrated that work boat exposure hours can be reduced by 70-80%, and a 14 streamer spread can be cleaned twice a week while acquiring seismic in all types of operating conditions.

  • Deep-seated focused fluid migration as indicator for hydrocarbon leads in the East Shetland Platform, North Sea Province

    Author: Jens Karstens, Philipp Müller, Christian Berndt, Stefano Patruno
    Geological Society London Special Publications SP494 - 1 July 2019

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    Hydrocarbon exploration in the North Sea Basin has revealed a multitude of focused fluid conduits, which manifest in seismic data as pipe or chimney structures that in some instances are connected to underlying hydrocarbon reservoirs. 3D seismic data from the eastern margin of the East Shetland Platform (ESP) reveal the presence of more than 450 focused fluid conduits. Most of these initiate at the Base Tertiary Unconformity (BTU) and crosscut the overlying sediments. The focused fluid conduits correlate with intra-platform basin structures beneath the BTU and with permeable sediments lobes, channels and deltaic units in the overlying Paleocene to Eocene successions, which include known hydrocarbon reservoirs (e.g. Bressay, Bentley, Skipper or Piper). Clusters of pipes associated with other channels and deltaic units may indicate the presence of additional prospects at the eastern margin of the ESP. Our study highlights the potential of using seismically imaged focused fluid system analyses in hydrocarbon exploration in platform areas on both sides of the Viking Graben and other frontier areas as they reveal the presence of working hydrocarbon charge pathways.

  • Improved HSEQ and Survey Efficiency Demonstrated with a New Remotely Operated Streamer Cleaning Tool

    Author: Trygve Skadberg, Rune Tønnessen, James Wright
    EAGE - 3 June 2019

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    Barnacle growth on seismic streamers creates noise on the recorded signals. Keeping a low noise level in barnacle areas is challenging to the seismic crews. Frequent workboat trips are required for streamer cleaning. Workboat operations are weather dependent and are considered undesirable from an HSE perspective. In 2007 a purely mechanical and autonomous Streamer Cleaner Unit (SCU) was introduced. The SCU is launched and recovered from the workboat. In 2016 Tønnessen and Skadberg (2016) presented a Remotely Operated Streamer Tool (ROST) capable of launching and recovering SCUs to/from the streamer without the use of a workboat, and which is less dependent on weather. The ROST is operated from a Support vessel. Experiences from four surveys are presented. Operation in high sea states is demonstrated on a survey offshore Namibia and operation in extreme currents demonstrated on another survey east of South Africa. A noise removal method is presented that allows operation of the system while online. The method was first applied on a survey offshore South Africa and later on two surveys offshore Angola. It is demonstrated that work boat hours can be reduced by 70-80%, and a 14 streamer spread can be cleaned twice a week while acquiring seismic.

  • 4D analysis, combining shallow hydrophone and multi-component streamer: the Cinguvu Field Offshore Angola example

    Author: Cyrille Reiser, Bruce Webb, Massimiliano Bertarini, Didier Lecerf, Vincenzo Milluzzo, Catia Rizzetto
    SEG - 14 October 2018

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    Efficiently and accurately estimating fluid-flow movement information from time-lapse data is a prime deliverable of any 4D acquisition and analysis. The key to success in this depends on a few factors including optimum 4D seismic
    acquisition, the seismic frequency bandwidth at the reservoir level and being able to deliver the 4D analysis or results in a very rapid and efficient manner. Maximum value of 4D is derived not from the data quality alone but also from the efficiency of delivering a 4D image and analysis. The value of the 4D decreases significantly with time, as results and analysis need to be delivered promptly to make an impact on the in-fill well program as well as on the reservoir development. From the 4D seismic image analysis (based on a calibrated broadband PSDM seismic processing), a dynamic warping algorithm was implemented for estimation of time-shift and delta velocity on this non-conventional typical “broadband” 4D seismic i.e. new multi-component over a conventional streamer legacy survey. The 4D analysis results were then compared with the 4D rock physics analysis at the available wells over the survey and related to the production-injection mechanism. This paper will review the project results and their impact in term of reservoir management understanding.

  • 4D Insights from SEG 2018

    Author: Andrew Long
    Industry Insights - 2 October 2018

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    The author reviews most of the SEG 2018 abstracts on 4D matters, with the exception of the more academic waveform inversion concepts unless they explicitly facilitate more efficient or flexible 4D data acquisition. This material is equally relevant for the ‘EAGE Australasian Workshop on Continuous Improvement in 4D Seismic’ which is held in Perth, Australia in the week immediately preceding the SEG 2018 annual conference.

  • Taking an integrated approach to seismic exploration

    Author: Patrick Coole
    Hart E&P - 1 April 2015

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    In 2014 Petroleum Geo-Services (PGS) began a large,integrated 2-D geosciences project with the aim of increasing the geological understanding of the Angolan and Namibian offshore margins. The project employed an integrated approach using regional 2-D interpretation, gravity and magnetics, and quantitative seismic interpretation to achieve this aim.

    Seismic acquisition took place offshore Angola in 2011 and offshore Namibia in 2013. Both datasets were acquired using PGS' dual-source GeoStreamer and GeoStreamer with GeoSource, respectively. The true broadband nature of this type of acquisition system allows a superior seismic image, providing broader frequencies across the amplitude spectrum and making it ideal for reservoir characterization/quantitative interpretation and geological interpretation.

    While shooting the seismic data, PGS also acquired gravity and magnetics data along the same lines. As such, the PGS Access project combines regional 2-D geological interpretation, quantitative interpretation, and gravity and magnetics. It also ties to important pre- and post-salt wells and discoveries, providing an integrated geoscience project targeted specifically at exploration and aiding geoscientists in understanding this prolific yet geologically complex margin.

  • Petroleum Prospectivity in the Namibe Basin, offshore Angola

    Author: Craig Koch, Jennifer Greenhalgh, Frances Mathew
    SEG - 23 September 2013

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    Recently acquired broadband 2D seismic from the Namibe Basin (offshore Angola) has allowed a detailed imaging of syn-rift and post-rift structures, enabling more confident identification and mapping of prospects analogous to those so prolific in the Santos Basin offshore Brazil. The improved imaging and resolution provided by these data significantly de-risk exploration in a frontier deepwater area where well costs are high.