[Opm] Wells being shut - "because it cannot get converged" for live oil, not dead oil
Tor Harald Sandve
tosa at norceresearch.no
Mon Jun 29 13:58:12 UTC 2020
Hi Stephan
Thank you for reporting the issue. The action of Shutting problematic wells were implemented some time ago to improve convergence. I agree that it may be a too drastic measure at least if the wells are closed pre-maturely. We have recently fixed some issues with this feature. What version of Flow are you running? Depending on your version there may be a runtime parameter called "--min-time-step-before-shutting-problematic-wells-in-days" You could try to run your case with a very small value for this parameter. i.e flow YOURCASE--min-time-step-before-shutting-problematic-wells-in-days=1e-12.
Tor Harald
[cid:norce_426cc920-64ab-4893-95d0-c29d5dab670c.png]
NORCE Norwegian Research Centre AS
norceresearch.no<https://www.norceresearch.no/>
________________________________
Fra: Opm <opm-bounces at opm-project.org> på vegne av Stephen, Karl D <K.D.Stephen at hw.ac.uk>
Sendt: fredag 26. juni 2020 15:28
Til: opm at opm-project.org <opm at opm-project.org>
Emne: [Opm] Wells being shut - "because it cannot get converged" for live oil, not dead oil
Hi,
I have a model being used as a well placement exercise (early stage) for waterflooding.
When run as a dead oil (PVDO is used but with a single Rs and live oil Bo and viscosity values), it seems to work fine. It even works OK if GAS (etc.) is added but the DISGAS keyword is left out.
However, for a proper live oil with DISGAS, a couple of the water injectors (placed down dip of the crest, on the fringe of the oil leg and in the water leg), get shut almost immediately from the start of the simulation and injection. The production wells are set to keep pressures above the bubble point (quite a bit) so the "dead oil" behavior should be replicated.
There is an "oscillation" warning and then several wells are shut and I am told that for each case the well " will be shut because it cannot get converged". A message follows: "Problematic wells were shut", and when I check the production summaries, they are shut for the rest of the simulation, which does proceed, albeit incorrectly. The permanent shutting of the wells seems a strange move for me - better to stop the simulation or try restarting the wells after a time step chop or equivalent. This suggests there's an issue with the code to me.
There's nothing particularly difficult about the injectors, they are vertical and placed in good perm cells and work for a dead oil anyway.
I think the problem is with calculating the RS. I read in a paper on OPM Flow that RS is the third variable when the simulation is above bubble point. I seem to recall spotting a problem like this on this help page a few months back or on GITHUB but can't find it relative to the problem I have. Maybe I was thinking of something different (there was one on convergence in cells).
I've played around with the numbers but I'm scratching my head. The wells were on pressure control and I tried setting to rate control and allowing greater BHP. Thinking the problem is related to injected water meeting live oil to calculate RS, I changed the completions to only inject below the OWC. This worked actually. What seems to be happening is that I need to get the pressure of the injector sufficiently large to get a converged solution. Changing completions reduced the WI of the well so that pressures went up. If I increase the rates I can then complete in the oil leg too.
Other LIVEOIL models have worked fine in different reservoir models so there's a combination of things going on here.
Any help gratefully received. I can forward models if necessary but would not post to the group as I need to send a zip file.
Karl
My PROPS and SOLUTION section are:
--======================================================================
PROPS
--=======================================================================
-- Oil Water Gas
DENSITY
52.6 64.0 0.1 /
-- Oil: Rs Poil Bo viscosity
PVTO
0.119 1160 1.312 0.570 /
0.454 1895 1.47 0.340
6950 1.307 0.58 /
/
PVDG
1160 2.738 0.0151
1444 2.17 0.01587
1729 1.786 0.01728
3000 1 0.02
4000 0.8 0.023
5000 0.75 0.026
6000 0.72 0.0285
7000 0.7 0.0305
/
-- Water: Pwat Bw Cw viscosity viscosibility
PVTW
5460 1.03 3.0E-6 0.34 0. /
-- Rock compressibility
ROCK
5111 3.0E-06 /
INCLUDE
'SWOFY.INC' /
--======================================================================
SOLUTION
-- Depth PB
RSVD
9000 0.454
10850 0.454 /
-- Initial conditions
-- Depth pressure OWC Pc at OWC GOC Pc at GOC Rs from RSVD table
EQUIL
10500 5700 10850 0.0 9000 0.0 1/
-- 10850 5694 10850 0.0 1* 0.0 1/
-- 10550 5775 10550 0.0 1* 0.0 1/
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