Creating a Spike Configuration will allow for parameters to be set for running a relative or absolute inversion.
- In the Spike tab, choose whether to apply the spike configuration to all wells at once or when curves are viewed.
- Click the Add icon (+) to add one or more spike configurations.
- To change the name of the Spike Configuration, double click on the name.
- Generate multiple configurations at once by clicking the icon on the left of the Add icon.
- In the Details Panel, configure the View Settings by selecting the interpolation method (i.e. Lagrangian or Nearest), fill, colour and size.
- Choose between an Absolute or Relative Spike Algorithm.
- Select the Low Frequency Inputs to use when running the inversion.
- Change Seismic Inputs to Volume to use the volumes specified in the Vol/Hors tab.
- At Stacks, select the stack volumes and their weights.
- The default wavelets are also the same ones specified in the Vols/Hors tab, although these can be overridden by selecting Override from the drop-down menu to select another wavelet.
- The defaults for the Spike Parameters are located in the Spike Defaults tab. If you have multiple spike configurations and would like to customise each one differently, select Custom (see below to define the spike parameters).
- When you are ready, click the Run Inversion icon in the Control Panel.
- In the Spike Defaults tab, select whether to use a horizon or constant to define the shallow and deep Spike Processing Horizons. If a horizon is chosen, a constant value can be used to offset the horizon.
- Similarly, select a horizon or constant to define the waterbottom for the Rock Physics AVA Covariance Constraint.
The Default Absolute Spike Parameters will apply unless they are manually changed.
- Notch: Defines the low frequency limit of the seismic used for inversion.
- Top End: Defines the high frequency limit of the seismic used for inversion
- Parameter Weights: A relative weight is assigned to each parameter. The default setting for most parameters is 100. Weights used for inversion can range higher or lower and should be determined from testing.
- Stack Weights: A relative weight can be assigned to a particular angle stack.
- Wavelet Scales: In Predict, the wavelet scalar can be multiplied to increase or decrease the wavelet scale used for inversion.
- Seismic Matcher: Solves for impedance variations to match the seismic AVA.
- LFM Matcher: Damps low frequencies not constrained by the seismic.
- HF Damper: Damps high frequencies not constrained by the inversion.
- Physical Property Bound Weight: Weighting assigned to physical property bounds (if used). These include bounds for Density, Vp/Vs and other properties.
Elastic stabilizations: Weights assigned to P-impedance vs Density (and/or S-impedance) cross correlation and variance.
- Default is 0, can be up to 10 or higher in some cases.
- Physical Property Bounds: Absolute values used to constrain physical properties. These parameters are optional but values used are typically a range just outside of observed values from well data.
- Rock Physics AVA Covariance Constraint: Defined using a rock physics model imported into Insight from a DUG Rock .trend file. This constraint uses depth-dependent end-member lithology rock properties for a background lithology to define the expected covariance of AVA coefficients.
The Default Relative Spike Parameters will apply unless they are manually changed.
- Vp/Vs: Defines a Vp/Vs ratio as an input for relative inversion.
- AVO0-AV01 Corrl'n: Defines intercept to gradient correlation as an input for relative inversion.
- AVO0-AVO2 Corrl'n: Defines intercept to curvature correlation as an input for relative inversion.