The purpose of this article is to explain Classify Subsurface Intervals.

To access Classify subsurface intervals:

1. Click the "Tools", Located on the top bar.  

2. Scroll down to "Subsurface"

3. Click "Classify subsurface intervals"


Prior to running the tool, you will need to load in XYZ points and grids.  A common application is to use wellbores as the XYZ input.  

Required Data tables 

  • Wellbore - Survey Data table 
  • Horizon - Formation Data table 

It is important to make sure that these 2 tables are in the same coordinate reference system. 


Annotates rows with X, Y, Z position with the associated interval, based on its vertical distance between the horizon grids.   

Classify Subsurface Interval Configuration: 

XYZ Input 

Data Table with rows to be annotated.  Can be wellbores, arbitrary XYZ points, or points along a wellbore

  • X - column with X location
  • Y - column with Y location
  • Z - column with Z location
  • Use active filtering - checked if XYZ points should be limited by active filtering


  • Data table - Table with the horizon or grid data
  • X - column with X location
  • Y - column with Y location
  • Z - column with Z location
  • Name - Unique identifier for each horizon, will be used as the interval annotation
  • Use active filtering - checked if horizons should be limited by active filtering
  • Automatic Update - automatically update the annotation if the filtering changes for either input tables


  • Result - Prefix to be used for annotation columns.
  • Transfer Columns (from XYZ inputs) - check the box to transfer XYZ inputs to new results columns.


XYZ points can only be classified if they lie within the interval between two grids.  In many cases, the XYZ points may fall outside the grids, which will return a null result.  Further, the user must make sure the units for both XYZ Input and Horizons are the same.

Steps to run:

  1. Go to the Tools menu
  2. Select Subsurface 
  3. Select the "Classify subsurface intervals" 
  4. Complete the classify subsurface interval configuration(above) and press OK

Outputs results: 

  • The outputs are new columns appended to the XYZ Input table, including:
    • Interval - Name of the closest horizon top
    • Interval Top - Distance (in Z units) to the closest horizon top
    • Interval Lower - Name of the lower horizon
    • Interval Btm - Distance (in Z units) to the closest horizon bottom
  • A Data Function is installed with provided inputs called "Interval Classifier".  You can "Edit Parameters" and change the properties for the function at a later time.   

    The classify subsurface intervals data function produces two outputs:
    • Columns are added to the wellbores table that indicates the zone for the well and distances to the closest top and bottom.
    • A new table will list all the distances to each horizon.
    • When you run the tool, you can transfer several columns from the Wellbore table.

For additional information on 3D Subsurface documentation, click here