ECLIPSE Convergence manual
This is a summary of ECLIPSE convergence issues. Most of the advice and suggestions apply equally to all the simulators.
ECLIPSE uses an iterative process based on Newton's method to solve the nonlinear equations.
The number of non-linear iterations is a guide to model convergence:
| Non-linears per Timestep | Guide |
| 1 | Very easy to converge |
| 2 to 3 | Easy to converge |
| 4 to 9 | Increasingly difficult flow situation |
| > 10 | Problem with model? |
Check the simulation reports. (see Background to timesteps and iterations). If the problem with:
- linear or non-linear iterations - check all warning messages for data problems
- timesteps - reduce when difficult modeling situations arise
- reports - request reports only when you need them
The greatest improvements in performance are obtained by identifying and correcting the cause of any nonlinear problems.
Controls available from the Schedule section:
- TUNING sets timestepping, iteration and convergence criteria
– TUNINGL is used for the LGRs in the model
Guidelines:
- Timestepping controls need alteration fairly frequently
- Iteration controls seldom need adjustment
- Convergence controls need adjustment only in highly unusual circumstance
Convergence problem Checklist
All sections
- Check all problem and warning messages.
- Does the model run better with no tuning keywords?
- Remove TUNING or TSCRIT or CVCRIT keywords and try to run.
- Is the model in equilibrium at the beginning of the simulation?
- Try running the model without any wells or any aquifers.
Grid and EDIT sections
- Use MINPV, check LIMITS, check LGRs.
- Check whether you need to set a minimum pore volume
- Radial runs: Is the inner radius too small?
- Dual porosity runs: Is sigma too large
- LGRs: Are the cells too small? In ECLIPSE 100 try LGRLOCK
PROPS section
- PVT data: Use EXTRAPMS in ECLIPSE 100. In all simulators, avoid PVT extrapolations
- SCAL data: Check the slopes of all relative permeability tables.
SOLUTION section
- Is initial fluid distribution stable?
SUMMARY section
- Remove RPTONLY
- Plot PERFORMANCE information
SCHEDULE section
- Avoid VFP table extrapolations, use EXTRAPMS in ECLIPSE 100.
- Take care when using MSWs
For more information and details, see the articles from the list below:
List of articles with details
Background to timesteps and iterations
How to speed up an ECLIPSE run
Eclipse Run Problems And Errors
Eclipse Severity Levels