Page 454 - KAPPA - Ecrin v4.30 tutorials

Ecrin v4.30 - Doc v4.30.01 - © KAPPA 1988-2013 Rubis Guided Session #7 • RubGS07 - 8/19
Fig. D01.4 • Initial phases and saturation pressure profiles corresponding to
a typical under-saturated oil zone (left) and to a saturated oil zone (right).
In order for the equilibrium condition at the GOC to be possibly met, one must ensure that the
chosen ‘Reference Initial Pressure’ at the corresponding reservoir temperature lies within the
critical point loci of all possible mixture of the chosen components.
In the present example, it occurs that Rubis will internally compute the following molar
compositions at the GOC:
%mol C2 %mol C10 %mol C12
Oil 0.5962 0.3028 0.1010
Gas 0.9390 0.0507 0.0103
In order to illustrate the consistency of the compositions computed at the GOC, one could go
back to the compositional PVT definition dialog and set in turns these two compositions as the
reference composition. Plotting the phase envelopes for these two compositions on top of each
other would lead to the plot presented in Figure D01.5. We can see from there that the
envelopes intersect at the specified GOC conditions. Care must then be taken in setting the
‘Reference Initial Pressure’ so that this condition can be met – in practice, Rubis will refuse to
proceed with the simulation step and issue a warning when the prescribed equilibrium occurs
to be impossible.