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@OWC GOC Pc@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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