Attribute Maps

Attribute maps can be generated both from observed seismic data and from modelled seismics. The definition of intervals for estimating attribute maps is controlled by a separate YAML file.

YAML File Section

Default values typically apply for attribute map generation in the sim2seis configuration file, as most information is derived from the dedicated interval definition file. Figure 1 shows the relevant sections of the configuration file. webviz_map refers to export of attribute maps in formats that can be read by webviz and ert for visualisation and history matching. As most parameters are commented out, this indicates that the default settings in most cases are used. It is only the name of the attribute definition file in the main class setting that must be specified. The settings for the observation error are given in the interval definition file and apply to observed data only.

# # Section for ert and webviz export
#______________________________________________________________________________________________________________________#
webviz_map:
  # grid_file: simgrid_maps4ahm.roff
  # zone_file: simgrid_maps4ahm--zone.roff
  # region_file: simgrid_maps4ahm--region.roff


## Section for seismic forward amplitude maps
#______________________________________________________________________________________________________________________#
# amplitude_map:
#  attribute: amplitude
#  pickle_file_prefix: amplitude_maps


## Section for seismic inversion relai maps
#______________________________________________________________________________________________________________________#
# inversion_map:
#  attribute: relai
#  pickle_file_prefix: relai_maps
#


## From the main class
#______________________________________________________________________________________________________________________#
attribute_map_definition_file: modelled_data_intervals_drogon.yml


## From path definitions:
# paths:
#   webviz_map_dir: sim2seis/input/attribute_maps

Figure 1: Parameters in the sim2seis configuration file related to attribute maps.

In addition, the file name for the interval definition file is specified in the main part of the configuration YAML
file:

attribute_map_definition_file: modelled_data_intervals_drogon.yml

Interval Definition YAML File

The interval definition file provides flexibility in defining intervals, resulting in a complex structure. Figure 2 illustrates the structure of the interval definition YAML file.

global:
  gridhorizon_path: share/results/maps # path for input horizons
  attributes: # attributes to be made for each cube
    - rms
    - mean
    - min
  scale_factor: 1.02
  surface_postfix: --depth.gri
cubes: # Setup for the cubes for which maps will be generated
  relai_depth: # arbitrary name of cube
    cube_prefix: seismic--relai_full_depth-- # start of observed cube name
    formations: # settings for each formation maps will be generated for
      volantis:
        top_horizon: topvolantis # Horizon used as top of the formation. ".gri" assumed as extension
        bottom_horizon: basevolantis # Horizon used as base of the formation ".gri" assumed as extension
        top_surface_shift: -5 # Extension of the window upwards from top surface
        bottom_surface_shift: 10 # Extension of the window downwards from bottom surface
        rms: # Special requirements for 'rms' attribute
          top_horizon: topvolantis
          bottom_horizon: basevolantis
          top_surface_shift: -15
          scale_factor: 1.05
  amplitude_depth: # arbitrary name of cube
    cube_prefix: seismic--amplitude_full_depth-- # start of cube name
    formations: # settings for each formation maps will be generated for
      volantis:
        top_horizon: topvolantis # Horizon used as top of the formation. ".gri" assumed as extension
        bottom_horizon: basevolantis # Horizon used as base of the formation ".gri" assumed as extension
        top_surface_shift: -17 # Extension of the window upwards from top surface
        bottom_surface_shift: -2
        mean: # Special requirements for 'mean' attribute
          top_horizon: topvolantis
          bottom_horizon: basevolantis
          top_surface_shift: -10
          bottom_surface_shift: -5
        min:
          scale_factor: 2.0

Figure 2: Parameters to define intervals for attribute map estimation.

Global Section

The global section defines parameters that apply to all interval definitions unless overridden later:

• Horizon path: Controlled by fmu-dataio, default value shown.
• Attributes: Select attributes to highlight important features in the 4D seismic.
• Scale factor: Used to match values in similar attributes from observed seismic data.
• Metadata fields: Used in fmu-dataio.
• Error settings: error and error_path define the observation error, see Error settings.

Error settings

The observation error is written as an OBS_ERROR column in the exported CSV files and applies to observed data only. It is defined by an error block with the following fields:

• type: relative (a fraction of the attribute value) or absolute (the error itself).
• value: a single scalar error, or
• error_surface: the name of a spatially varying error map, resolved against the global error_path. The file is read with xtgeo and must have the same geometry as the attribute maps. Exactly one of value or error_surface must be given.
• minimum: an absolute floor applied after the error is computed (default 0.0).

All four combinations of type and source (scalar value or error_surface) are supported. The error_path directory is set once, in the global section only.

The error block can be given at the global, cube, or formation level. A block at a more specific level fully replaces the one at the level above it (whole-block replacement); individual fields are not merged. For example:

global:
  error_path: share/results/maps
  error:
    type: relative
    value: 0.07
    minimum: 0.005
cubes:
  relai_depth:
    error: # replaces the global error for this cube
      type: absolute
      error_surface: relai_error.gri
      minimum: 0.005
    formations:
      volantis:
        error: # replaces the cube/global error for this formation
          type: relative
          value: 0.05

Cube Section

• Cube names: Arbitrary values.
• Cube prefix: Concatenated with seismic difference dates defined in the global config file.
• Seismic path: Controlled by fmu-dataio, default value shown.
• Vertical domain: Default is depth.

Formations Section

Several formations can be defined under each cube. Interval settings apply to all attribute calculations listed in the global section unless specific values are set. Intervals can be defined in two ways:

1. Top and Base Horizon: Specify the top and base horizons, with optional shifts for each.
2. Top Horizon and Interval Length: Specify the top horizon and the interval length, with an optional shift of the top horizon.

For example:

• For relai_depth cubes:
  • min and mean are calculated from Top Volantis shifted 5 ms up to Base Volantis shifted 10 ms down.
  • rms is calculated from Top Volantis shifted 15 ms up to Base Volantis.
• For amplitude_depth cubes:
  • mean has a separate interval definition from rms and min.
  • min has a different scaling factor than the others.