This commit adds support for assigning the initial phase pressure
distribution to a subset of the total grid cells. This is needed in
order to fully support equilibration regions. The existing region
support (template parameter 'Region' in function 'phasePressures()')
was only used/needed to define PVT property (specifically, the fluid
phase density) calculator pertaining to a particular equilibration
region.
This commit adds a simple facility for calculating initial phase
pressures assuming stationary conditions, a known reference pressure
in the oil zone as well as the depth and capillary pressures at the
water-oil and gas-oil contacts.
Function 'Opm::equil::phasePressures()' uses a simple ODE/IVP-based
approach, solved using the traditional RK4 method with constant step
sizes, to derive the required pressure values. Specifically, we
solve the ODE
dp/dz = rho(z,p) * g
with 'z' represening depth, 'p' being a phase pressure and 'rho' the
associate phase density. Finally, 'g' is the acceleration of
gravity. We assume that we can calculate phase densities, e.g.,
from table look-up. This assumption holds in the case of an ECLIPSE
input deck.
Using RK4 with constant step sizes is a limitation of this
implementation. This, basically, assumes that the phase densities
varies only smoothly with depth and pressure (at reservoir
conditions).
This is intentionally black-oil specific because we presently do no
know how to handle other cases (e.g., more phases or number of phases
different from number of components).
The second input of initBlackoilStateFromDeck that computes surface
volumes based on gas/oil ratio is changed from
BlackoilPropertiesInterface to Props. To avoid duplication with the old
initBlackoilStateFromDeck its name is changed to
initBlackoilSurfvolUsingRS.
Add new function is added that computes saturation from surface volumes
solving z = As for each cell. This function is used to compute an
intial guess to the saturations in initState_impl.hpp.
The 'comp_term' is supposed to be a total divergence term, which is supposed
to be zero for incompressible flow. It was added for improved robustness in
stagnant areas, but as implemented it would not be computed properly for
oil injection scenarios, due to the convention for two-phase transport
source terms (positive terms are inflow of first phase [water], negative
terms are total outflow).
The WellsManager class handles INJECTORS by assigning a phase
distribution (W->ctrls[i]->distr) that coincides with the injected
fluid for the corresponding well (e.g., {1,0,0} for WATER injectors in
a three-phase WATER/OIL/GAS simulation). This, however, meshes poorly
with the restriction that all phase components must be ONE in the case
of wells constrained by total reservoir volume flow targets (RESV)
that was introduced in commit b7d1634.
This change-set limits the restriction on phase distributions to
PRODUCERs only and is a tentative solution to GitHub PR #360.
