PPP: Hints and Troubleshooting

1D well calibration mode (Pore Pressure Prediction view)

If a curve on any track is not showing, the first thing to check is whether it is enabled for display in the View tab or the right-click Configure Track dialog.

Typical Cause(s)
No well(s) in list
Well(s) is de-selected in main control panel
Toggle green light of said well(s) in Insight control panel Well tab.
No log curves shown
a) Well(s) is not selected
b) No curves assigned
c) View window outside long zone
d) Curve(s) units incorrect
a) Choose from drop-down
b) Under Well Settings, define curve data
c) Right-click any track, select Zoom to fit.
d) Ensure relevant curves in well are assigned correct class and units in main control panel, Well tab
3 Extrapolated density not showing Under OBP tab, Use density from volume is selected (note: that to view Density from volume curve, switch on Density volume in the View tab) Under OBP tab, ensure Specific density settings for well is set as Use density from well log (also ensure Extrapolated Well Curve is enabled in the View tab)
4 Overburden pressure gradient not showing Use density from volume is selected and density volume is in error Check main control panel, Process tab, PP: Density Volume is correct (common error is a missing Calculation Layer Top depth or horizon - usually waterbottom - as show in figure 28(c)).
5 Normal compacting trends not showing a) As Constant or Formula - is not or incorrectly entered
b) As Picked curve - is not created
c) As Log curve - is not assigned
a) Check NCTL constant formula is valid and within the track display limits
b) Set NCTL Method as Picked and on DT/RES track right click to Start/Stop picking NCTL
c) Ensure a relevant NCTL curve exists for the well, with sonic units and assign
6 Smoothed sonic log (OSTCL - Observed Shale Compacting Trend Line) not showing No shale indicator points picked On shale indicator track, right-click to Start picking Shale Cutoff to cover the length of sonic
7 No pressure curves shown a) No OBP set
b) No NCTL set (DT/RES/vel)
c) No OSCTL is generated
d) No velocity volume is chosen
a) Ensure OBP calculated (issue 3 & 4)
b) Ensure NCTL exists (issue 5)
c) Ensure shale indicator points are picked
d) Ensure velocity volume selected in Pore Pressure tab (or in Configure Time/Depth Conversion)
8 Well calibration points not showing a) Group is not visible
b) Units are mismatched 
a) Toggle green light on in either the Calibration Points tab or right-click Configure Track dialog
b) Ensure units selected for group on Calibration Points tab matches the units of imported data.
9 Well markers not showing a) No markers in well
b) Markers track is off
c) Well markers not checked
a) Check well configuration, Markers tab
b) View tab, Markers tracks, toggle green light on
c) View tab, Annotations, Well Markers check on

3D model building mode

Typical Cause(s)
Density volume won't calculate a) Volume type is not interval velocity in depth
b) Calculations Layer is not set
a) Use process Velocity Conversion
b) Choose an appropriate depth horizon or depth value below which the GGG velocity-to-density transfer equation will apply
Well logs not showing a) Well is off
b) Density and/or wiggle curve not enabled
c) Desired curve has been assigned incorrect class or units
a) Control panel, Well tab, click green light on
b) Enabled either Show density display and/or Show wiggle display
c) Ensure that the appropriate Class and units are selected for the desired well(s) and curves

Pore pressure logs don't match model a) Eaton parameters from the 1D well calibration don't match the 3D process.
b) Global well class has assigned wrong pressure curve
a) Ensure all global Hydrostatic Gradient, Velocity Exponent, and Velocity NCTL are copied from the PPP well calibration module (not from the per-well Override values)
b) Switch off global well class; select desired curve from main control panels; switch global class back to Pore Pressure

Unit conversions

The View tab allows the pressure gradient track to be in units of pounds per gallon (ppg) or specific gravity (SG). For reference, the conversion factor is:

	SG = ppg / 8.3

The pressure track is fixed in pounds per square inch (psi).

For reference, the conversion from ppg to psi is:

	psi = (tvdss_m / 0.3048) * (0.052 * ppg) = (tvdss_m / 0.3048) * (0.052 * 8.3 * SG)

References and further reading

Traugott, M.O. and Heppard, P.D., 1997 Pore/Fracture Pressure Determinations in Deep Water: Deep Water Supplement to World Oil.

van Ruth, P., Hillis, R. and Tingate, P., 2004, The origin of overpressure in the Carnarvon Basin WA - implications for pore pressure prediction, Petroleum Geoscience, 10, 247–257.

Yardley, G.S. and Swarbrick, R.E., 2001, Lateral Transfer: A source of additional overpressure: Marine and Petroleum Geology.

Zhang, J., 2011, Pore pressure prediction from well logs: Methods, modifications and new approaches, Earth-Science Reviews, 108, 50–63.