DUG Insight User ManualFrequently Asked QuestionsFrequently Asked Questions HorizonsHow do I extract the number of events between 2 time horizons?

How do I extract the number of events between 2 time horizons?

Use this workflow to calculate a rough estimate for event counts, based on average frequency and time thickness of the target zone. This example calculates the seismic event counts from TopRes to BaseRes horizons for a 3D seismic volume in time.

Step1: Create an  instantaneous frequency for stack:

  1. Go to Control panel > Process and add an Instantaneous Attributes process
  2. Select the volume.
  3. Select the Frequency checkbox.

Step 2: Calculate average of instantaneous frequency (Ave_IF) from the top to bottom horizon:

  1. Go to Control panel > Map view.
  2. Click the Operations tab and select Amplitude Extraction from the Operation dropdown menu.
  3. Under Horizons, use this configuration:
    • Top: pick Horizon from the dropdown and select the top horizon e.g. TopRes.
    • Bottom: pick Horizon from the dropdown and select the bottom horizon e.g. BaseRes.
  4. Use the created volume from the Instantaneous Attributes process e.g. instantaneous attributes: frequency.
  5. Use Simple Average as the property.
  6. Click Run.

Step 3: Calculate time thickness from the top to bottom horizon:

  1. Calculate time thickness from the top to bottom horizon:
  2. Go to Control panel > Map view.
  3. Click the Operations tab and select Horizon Maths from the Operation dropdown menu.
  4. Add 2 symbols by clicking the blue "+" button and set:
    • h1: top horizon e.g. TopRes
    • h2: bottom horizon e.g. Base Res
  5. Use formula: h2 - h1.
  6. Click Run.

Step 4: Calculate Number of events from top to bottom horizon:

  1. Go to Control panel > Map view.
  2. Click the Operations tab and select Horizon Maths from the Operation dropdown menu.
  3. Add 2 symbols by clicking the blue "+" button and set:
    • h1: the calculated average of instantaneous e.g. Ave_IF
    • h2: the calculated time thickness e.g. Thickness_time
  4. Use formula: Ave_IF x (Thickness_time / 2000) or h1 * (h2 / 2000).
  5. Click Run.

The results can be QC with the Event counts graphed on top of the seismic section by writing the results from step 4 to one of the unused header in the seismic:

  1. Go to Control panel > Process.
  2. Click the blue "+" button and add a Header Maths process.
  3. Select the seismic in the Volume search box.
  4. Add a new symbol by clicking the blue "+" button.
    • Select the "Event counts" horizon as h1.
  5. Add a new header formulae by clicking the blue "+" button:
    • Select header: 105 laga: SEG-D Skew.
    • Use formula: if (isnan(h1), nan, h1).

Note: To QC this event, use the IL/CL view and enable header graphs.