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XML Model | Inversion | Estimation | Forward modelling | Rock Physics | Facies Predictions

Running CRAVA is based on xml files. A single xml file is used with a CRAVA run and it contains all information regarding input files, different settings and output results. These files must be edited with a text editor / xml editor.

All keywords starts and ends with a tag, e.g. <crava> and </crava>.

The CRAVA user manual contains list of all available keywords and a description of each.

Examples of the xml files can be downloaded in the Download page, which can be used as a starting point when setting up a CRAVA model.

Main keywords examples

Actions

Specifies running mode (inversion, estimation or forward model), and whether it is a prediction or simulation run.

<actions>
  <mode> inversion </mode>
  <inversion-settings>
    <prediction> yes </prediction>
  </inversion-settings>
</actions>

Survey

Survey keyword is used for specifying the seismic data and wavelets.

<survey>
  <angle-gather>
    <offset-angle> 16 </offset-angle>
    <seismic-data>
      <file-name> SeismicCube16.segy </file-name>
    </seismic-data>
      <wavelet>
        <file-name>wavelets/Wavelet_16.0deg.wlt  </file-name>
      </wavelet>    
  </angle-gather>
</survey>

The wavelet can be given from file (as shown), or be estimation (no <wavelet> keyword), or it is possible to use a ricker wavlet (with a <ricker> keyword instead of <file-name>).

Under <wavelet> it is also possible to give a <scale> value to scale the wavelet from file or ricker, or Crava can estimate the scale by using <estimate-scale>.

Well-data

Specifies input wells and the log names.

<well-data>
  <log-names>
    <time>     TWT    </time>
    <dt>          DT      </dt>
    <dts>        DTS    </dts>
    <density> RHOB </density>
  </log-names>
  <well>
    <file-name> Well1.rms </file-name>
  </well>
</well-data>

Crava supports both rms and las wells. Each well can also be specified if what it should be used for with the keywords <use-for-wavelet-estimation>, <use-for-background-trend>, <use-for-facies-probabilities> and <use-for-rock-physics>.

Prior-model

Information about the prior-model, background, correlation, correlation-directions, facies probabilities and rock-physics is specified under <prior-model>

<prior-model>
  <background>
    <high-cut-background-modelling> 6 </high-cut-background-modelling>
    <lateral-correlation>
      <variogram-type> genexp </variogram-type>
      <range>        2000 </range>
      <subrange>  1000 </subrange>
      <angle>            70 </angle>
      <power>             1 </power>
    </lateral-correlation>
    <correlation-direction>
      <top-conform> yes </top-conform>
    </correlation-direction>
  </background>
</prior-model>

The background model can either be estimated (as above), given from file (<vp-file>), a constant value (<vp-constant>) or taken from rock physics.

Correlation settings are also set her. These include <lateral-correlation> variogram, <correlation-direction> as shown above. Also <parameter-correlation> and <temporal-correlation> can be given here, if they should not be estimated by Crava.

<facies-probabilities> can be given under <prior-model>, where <prior-probabilities> and <volume-fractions> can be given.

<rock-physics> is also specified here. The base structure of the rock physics template consists of the elements <reservoir>, <evolve>, <predefinition>, <rock> and <trend-cube>, each of which contains sub-elements. The sub-elements will be basic building blocks (e.g. <solid>, <fluid>, <dry-rock>), properties (e.g. temperature, pore-pressure, density, etc) and theories.

Project settings

Specifies output/inversion volume and other input/output-settings. The area can be utm-coordinates, inline-crossline-number or taken from a surface. The volume is specified either with interval-one-surface (and a thickness), interval-two-surface or multiple interval.

<project-settings>

  <output-volume>
   <utm-coordinates>
      <reference-point-x>  1000 </reference-point-x>
      <reference-point-y>  5000  </reference-point-y>
      <length-x>                4500  </length-x>
      <length-y>                4500  </length-y>
      <angle>                          0  </angle>
      <sample-density-x>       50 </sample-density-x>
      <sample-density-y>       50 </sample-density-y>
    </utm-coordinates>

  <interval-two-surfaces>
      <top-surface>
        <time-file>   TopSurface.storm </time-file>
     </top-surface>
      <base-surface>
        <time-file>   BaseSurface.storm </time-file>
      </base-surface>
      <number-of-layers>   100 </number-of-layers>
    </interval-two-surfaces>
  </output-volume>

  <io-settings>
    <input-directory>    input/   </input-directory>
    <output-directory>  output/ </output-directory>

    <grid-output>
      <format>
        <storm>    yes </storm>
        <ascii>       no  </ascii>
      </format>

      <elastic-parameters>
        <vp>                 yes </vp>
        <vs>                 yes </vs>
        <density>         yes </density>
        <background>   yes </background>
      </elastic-parameters>
    </grid-output>

   <well-output>
      <blocked-wells> yes </blocked-wells>
    </well-output>

    <wavelet-output>
      <format>
        <jason> yes </jason>
      </format>
      <well-wavelets>    yes </well-wavelets>
      <global-wavelets> yes </global-wavelets>
    </wavelet-output>

    <other-output>
      <prior-correlations> yes </prior-correlations>
    </other-output>

  </io-settings>
</project-settings>