PPP: Hints and Troubleshooting
Common issues and solutions are shown below. For additional help, please email [email protected].
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.
|
No. |
Issue |
Typical Cause(s) |
Solution(s) |
|---|---|---|---|
| 1 |
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. |
| 2 |
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
|
No. |
Issue |
Typical Cause(s) |
Solution(s) |
|---|---|---|---|
| 1 |
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 |
| 2 |
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 / 8.3The 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.