Linear Model view

Use the Linear Model view (Pore Pressure > Compaction Analysis > Linear Trends > Linear Model) to observe and edit linear trend line segment properties. All available linear trend lines are visible in this view. You also can choose the method to calculate the pore pressure: Eaton, Ratio, Equivalent depth. For more information about these methods, see Theory and equations.

     click to enlarge

Each line has the following information:

  • Lock Segment (toggle)
  • Start TVDSS
  • Stop TVDSS
  • Start Value
  • Stop Value
  • Unit
  • Calculation Method
  • Eaton Exponent
  • Correlation Factor
  • Edit Slope (toggle)
  • Slope
  • Unit

Changing the start and stop depths

To change the start and stop depths, double-click in the appropriate box to select the current value and then type the new value. Because by default you maintain the slope, when you modify the start depth, the end depth is automatically updated.

Notice that, by default, the edit slope option in the NCT table is not checked. Therefore, whenever you change the start TVDSS or end TVDSS point, the application immediately modifies the end TVDSS /start TVDSS point accordingly, to maintain the slope value. If you check the edit slope column, then the start TVDSS and end TVDSS point is read-only and only the log stop value is modified.

The application does not allow overlapping line segments, so if you wish to increase the stop depth of an upper segment, you must first increase the start depth of the next deeper segment to prevent overlap.

Changing the calculation method

The method used to calculate the pore pressure from the linear trend is shown in the Calculation Method column. The methods include Eaton, Ratio, and Equivalent Depth. To change the method, click the current method and select a different method. There is an option to select Eq Depth and Eaton at the same time. For more information about these methods see Theory and equations.

Locking the slope of a segment

To lock the slope of any segment, check the Lock Segment box. The fields in the table become read-only and the linear trends points in the Well View turn green. You can no longer adjust the segments nor the line.