Smoothing logs

With the Smooth Logs option under the Log Tools button (Prepare > Wells > Log Tools) you can create an averaged log based on log values within a (user-defined) window length. Smoothing can only be applied to continuous logs. On the form you can optionally select a (secondary) discrete log and use its property class intervals (also called zones below) to confine the averaging to each zone. You can smooth a particular log (e.g. a porosity log) for multiple wellbores in one go.

Smoothing logs can be used, for example, to generate an averaged log which may represent a vertical facies trend. If the averaged log values are then ‘translated’ into a facies property and laterally interpolated, the data can be used as a property in facies modeling.

To smooth a log

1. Open the Smooth Logs form (Prepare > Wells > Log Tools) in the Log Tools section of the strip.

2. Enter the required data:

   Source log  Name of the log for which values are to be smoothed. Smoothing can only be applied to continuous logs. All continuous logs in your Well Data folder are listed in the drop-down list.

   Well group   If you have a well group in the Well Data folder, you can select it. It will act as a filter on the wellbore list. Note that the selected log will be smoothed for the selected wellbore(s) in all well groups where the wellbore(s) exists (including 'All wells'), not only in the selected well group.

   Wellbores  In the list, select the wellbore(s) for which you want to smooth the selected log.. Only wellbores that have the selected log are listed.

   Window length  Specify the interval, in MD, over which averaging will be carried out. The averaged value is assigned to the midpoint position of the entire window.

   Interpolation method  To properly calculate average log values, the log is resampled with a regular increment (0.5 ft) during which interpolation is performed. Resampling is especially necessary when the log is irregular, i.e. log values are irregularly spaced. The Interpolation method defines how the interpolated values are calculated.

   Linear, i.e. value defined by distance to two neighboring data points

   Cubic, i.e. value defined by 4 neighboring data points (two at each end, more continuous result).

   Deal with edges  Define how the averaging proceeds at the end of averaged log segments and, if the ‘Per zone property class’ checkbox is checked, at zone boundaries.

   Fixed length: The averaging window is kept at its fixed length. Values in the window belonging to another zone, are ignored, still the averaged value is assigned to the midpoint position of the entire window. When the midpoint position is (almost) at the zone boundary, the averaging window is still about half the window length.

   Rescale smoothing window: When the averaging window reaches a zone boundary it is rescaled and averaging takes place over an increasingly smaller window length. The averaged value is assigned to the midpoint position of the resized window.

   The ‘Fixed length’ option will, in general, create a sharper boundary in the averaged log.

   Per zone property class  Check this checkbox to create a log of source log values averaged per zone. Zones are defined by the discrete log values of the log that you select from the drop-down list (only discrete logs are listed, e.g. facies log, fluid log, etc.). In intervals where the discrete log is non-existent, the smoothed log will be non-existent as well.

   Log suffix  The new log is created with the specified name <name of the source log>_Smoothed, but you can change it if you want. If you remove the suffix entirely, the source log will be overwritten, but you will be prompted with a warning first.

3. Click Apply or OK to complete the log smoothing. The new log will be created for the individual wellbores under Well Data > Wells, and can also be found under Well Data > All Logs.