[Opm] Wells being shut - "because it cannot get converged" for live oil, not dead oil

[Stephen, Karl D]

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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