Sigmalog input

The Sigmalog Input form (1D Model > Pore Pressure > Sigmalog Input) takes drilling inputs such as ECD, RPM and ROP to calculate the Corrected Sigmalog. Based on the aim of your study and the data available, you can choose to use either an ECD or Mud Weight log as the input, and can also choose between using a hydrostatic pore pressure constant or gradient. The resulting Corrected Sigmalog then undergoes shale and boxcar filtering in the next form, Sigmalog Filtering.

To calculate the Corrected Sigmalog

  1. Specify either an ECD or Mud Weight log as input. By default, an ECD log can be specified and the Mud Weight field is locked. If you wish to use a Mud Weight log instead, select  Mud Weight for the Calculate using parameter. This will lock the ECD field and allow you to specify a Mud Weight log.
  2. Select the input logs for RPM, ROP, WOB and Bit Size; all selections need to be made in order to calculate the Corrected Sigmalog.
  3. For Hydrostatic PP, the default use is to define a constant value. If you have a hydrostatic pore pressure gradient that you prefer to use, uncheck the box for Calculate hydrostatic pore pressure using fluid density and choose a log in the Hydrostatic PP field.
  4. Optionally, you can correct for shallow sediments above a defined TVDRT. To do so, check the Use correction for shallow sediments above TVDRT box and specify a depth.
  5. After you have specified the inputs and calculation options, click (Re)Calculate to calculate the Corrected Sigmalog, then click OK to proceed to the Sigmalog Filtering form.
To change the default name of the created log, double click in the log field. The background turns blue, indicating you can edit the text. When done, click the green check mark to apply the changes.