Assessing impact of velocity uncertainty on structural models using GeoChron

Anne-Laure Tertois and Romain Merland and Damien Foissard and Jean-Laurent Mallet. ( 2020 )
in: 2020 RING Meeting, ASGA

Abstract

Between data acquisition and first oil or gas", a number of conventional workflows produce information which helps decision makers to define the best possible reservoir engineering parameters for production. Data are processed, imaged, migrated, interpreted, modelled, gridded and fed to flow simulators to perform reservoir assessments. Each of these steps comes with its own attached uncertainty which is often not propagated and considered all along the workflow. \\ \\Uncertainty evaluation is already a strong part of reservoir characterisation at the rock property modelling stage. Assessing uncertainty on reservoir structure, one step earlier in the workflow, is still not standard in our culture because of the complexity of such a task. \\ \\Relying on the strength of describing a structural model as a consistent volume linked to the depositional space, the GeoChron framework offers a theoretical background in which each source of uncertainty can be analysed, modelled independently and integrated consistently into different realisations of a structural model. For a number of years, uncertainty on fault and horizon picking, as well as fluid contact positions, has been part of the structure uncertainty modelling workflow based on the GeoChron theory.\\ \\Before horizons and faults can be picked, seismic data has to be imaged and migrated to create a representation of the subsurface. Those complex processes rely on a velocity model which is, in itself, uncertain. In this paper, we show how uncertainty on the velocity model can be very simply integrated by geomodellers into the structural uncertainty modelling workflow without requiring extensive geophysical knowledge. We validate the approach by comparing results from this velocity uncertainty method to time to depth conversions using velocity models which have been altered to reflect the same shifts in velocities. Finally, a case study shows how velocity uncertainty modelling can be integrated in the current structural uncertainty workflow, thus helping to start considering uncertainty around the velocity model and hopefully leading to further integration with geophysical tools such as tomography.\\

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    BibTeX Reference

    @INPROCEEDINGS{TERTOIS_RM2020,
        author = { Tertois, Anne-Laure and Merland, Romain and Foissard, Damien and Mallet, Jean-Laurent },
         title = { Assessing impact of velocity uncertainty on structural models using GeoChron },
     booktitle = { 2020 RING Meeting },
          year = { 2020 },
     publisher = { ASGA },
      abstract = { Between data acquisition and first oil or gas", a number of conventional workflows produce information which helps decision makers to define the best possible reservoir engineering parameters for production. Data are processed, imaged, migrated, interpreted, modelled, gridded and fed to flow simulators to perform reservoir assessments. Each of these steps comes with its own attached uncertainty which is often not propagated and considered all along the workflow. \\ \\Uncertainty evaluation is already a strong part of reservoir characterisation at the rock property modelling stage. Assessing uncertainty on reservoir structure, one step earlier in the workflow, is still not standard in our culture because of the complexity of such a task. \\ \\Relying on the strength of describing a structural model as a consistent volume linked to the depositional space, the GeoChron framework offers a theoretical background in which each source of uncertainty can be analysed, modelled independently and integrated consistently into different realisations of a structural model. For a number of years, uncertainty on fault and horizon picking, as well as fluid contact positions, has been part of the structure uncertainty modelling workflow based on the GeoChron theory.\\ \\Before horizons and faults can be picked, seismic data has to be imaged and migrated to create a representation of the subsurface. Those complex processes rely on a velocity model which is, in itself, uncertain. In this paper, we show how uncertainty on the velocity model can be very simply integrated by geomodellers into the structural uncertainty modelling workflow without requiring extensive geophysical knowledge. We validate the approach by comparing results from this velocity uncertainty method to time to depth conversions using velocity models which have been altered to reflect the same shifts in velocities. Finally, a case study shows how velocity uncertainty modelling can be integrated in the current structural uncertainty workflow, thus helping to start considering uncertainty around the velocity model and hopefully leading to further integration with geophysical tools such as tomography.\\ }
    }