EOS COMP
When in COMP mode, the EOS COMP table is available to specify EOS properties for the various components. The equation of state used is always cubic. This replaces EOS OIL and EOS GAS.
An example of the table is as follows:
EOS COMP
PREOS
GCOND
CNAME CO2N2 C1 C2 C3 C46 C7P1 C7P2 C7P3
TCRIT K 215.2 186.6 305.4 369.9 396.2 572.5 630.2 862.6
PCRIT Bar 53.903 45.6 46.20 42.55 34.35 25.93 16.92 8.61
ZCRIT 0.283 0.224 0.285 0.281 0.274 0.260 0.260 0.260
ZMF Frac 0.0315 0.6599 0.0869 0.0591 0.0967 0.0472 0.0153 0.0034
ACF 0.1325 0.013 0.098 0.152 0.234 0.332 0.495 0.833
MW 36.01 16.04 30.07 44.10 67.28 110.9 170.9 282.1
BIC 0.036
BIC 0.05 0
BIC 0.08 0 0
BIC 0.1002 0.09281 0 0
BIC 0.1 0 0.00385 0.00385 0
BIC 0.1 0 0.00630 0.00630 0 0
BIC 0.1 0.1392 0.00600 0.00600 0 0 0
END
It is possible to enter the EOS COMP input defaulting some single component properties. This can be done using a Def (or Default) string, or by ending a line of values early using a / character, for example:
EOS COMP
PREOS
CNAME CO2 C1 C2 C3 C46 C7P1 C7P2 C7P3
TCRIT K Def Def Def Def 396.2 572.5 630.2 862.6
PCRIT Bar Def Def Def Def 34.35 25.93 16.92 8.61
ZCRIT Def Def Def Def 0.274 0.260 0.260 0.260
ZMF Frac 0.0315 0.6599 0.0869 0.0591 0.0967 0.0472 0.0153 0.0034
ACF Def Def Def Def 0.234 0.332 0.495 0.833
MW Def Def Def Def 67.28 110.9 170.9 282.1
END
If a default is requested, the data will be taken from an internal library for the following recognised components:
H2, H2O, H2S, CO2, N2, C1, C2, C3, C4, IC4, C5, IC5
If all the components used are in this set they can be defaulted, or a line of properties omitted:
EOS COMP
PREOS
CNAME CO2 C1 C2 C3
ZMF Percent 80 20 /
END
The binary interaction coefficients default to zero; but if non-zero ones are required a full set of BIC values are required.
If components are specified (such as those above C5) then values must be entered, except for the ideal gas specific heat coefficients, CPIGA to CPIGE. Default values are provided in this case for all components, either from the library, or from a correlation with respect to molecular weight.
The actual properties used, and the properties of the library components, are printed in the .out file, under the headers:
== EOS SCP==============================================================================
== EOS CIPG=============================================================================
== LIBRARY==============================================================================
== LIB CIPG=============================================================================
The sub-keywords in EOS COMP are described below:
PREOS
Specify to use the Peng-Robinson equation of state [PR76].
SRKEOS
Specify to use the Soave-Redlich-Kwong equation of state.
CNAME
Followed by a set of component names. If not supplied, internal names like C1, C2 will be generated.
TCRIT
Component critical temperatures. Followed by unit (K is only option at present). Then Nch values, where Nch = Nc-1 is the number of non water components.
PCRIT
Component critical pressures. Followed by pressure unit (e.g., Bar), then Nch values.
ZCRIT
Component critical Z-factors. No unit; followed by Nch values.
ZMF
Reservoir non-aqueous phase composition. Followed by unit (Frac or Percentage), then Nch values. The composition can be over-ridden on a cell by cell basis using ZMFVD.
ACF
Component acentric factors. No unit; followed by Nch values.
PRCORR
This keyword activates a modification of the acentric factor polynomial in the Peng-Robinson equation of state [PR76]. For acentric factor w > 0.49 a cubic expression is used instead of the quadratic default.
MW
Component molecular weights. No unit; followed by Nch values.
SHIFT
Component dimensionless shift factors for the Peneloux volume shift.
OMEGAA
Non-default Omega A values for the equation of state.
OMEGAB
Non-default Omega B values for the equation of state.
BIC
Binary interaction coefficients. As series of keywords specifying the binary coefficients as a lower triangular matrix. So the first BIC will specify the binary interaction coefficient between component 2 and component 1; the next BIC will specify the two binary interaction coefficients between component 3 and components 1 and 2, and so on – a total of \(N_{ch}(N_{ch}-1)/2\) values are required.
GCOND
Specifies a gas condensate reservoir (all one phase hydrocarbon states are gas).
PARACHOR
Parachors are values which can be used in the McLeod-Sugden expression for surface tensions [Sug24]. Parachors have units of \((dynes/cm)^{1/4}cm^3/mol\) or \((mN/m)^{1/4} cm^3/mol)\), as 1 mN/m = 1 dyne/cm. Typical values are of the order of 100. This is a conventional unit for the parachor, and PARACHOR values will always be regarded as being in these units.
Parachors are entered as part of the equation of state description in COMP EOS mode, and take the form, for example, of:
EOS COMP
PREOS
CNAME C1 C3 C6 C10 C15 C20
...
PARACHOR 71 151 271 400 600 800
END
PARACHOR values are only required with the MISCIBLE option activated.
LBCCOEF
This keyword allows to reset the coefficients of the Lorentz-Bray-Clark viscosity correlation.
LBCCOEF is followed by 5 values. For example:
LBCCOEF 0.102 0.0234 0.058 -0.0407 0.00934 /
It is possible to set a default with the Def value or an early / terminator:
LBCCOEF 0.1 Def /
The five default values are:
0.1023, 0.023364, 0.058533, -0.040758, 0.0093324
SWEOS for Søreide-Whitson EoS
This is a new compositional equation of state for 1.9. It is a three phase cubic equation which describes oil, water and aqueous phases within a single model.
The equation is described in [SoreideW92].
To use the Søreide-Whitson EoS the COMP or COMP3P mode must be selected:
SUBSURFACE_FLOW Flow
MODE COMP3P 9 EOS ! 9 Total, 8 hydrocarbon + water in the SW EoS
The SW equation must be selected in the EOS COMP section using the SWEOS keyword:
EOS COMP
SWEOS
PRCORR
CNAME CO2N2 C1 C2 C3 C46 C7P1 C7P2 C7P3 H2O
TCRIT K 215.2 186.6 305.4 369.9 396.2 572.5 630.2 862.6 647.1
PCRIT Bar 53.903 45.6 46.20 42.55 34.35 25.93 16.92 8.61 220
ZCRIT 0.283 0.224 0.285 0.281 0.274 0.260 0.260 0.260 0.2294
ZMF Frac 0.0315 0.6599 0.0869 0.0591 0.0967 0.0472 0.0153 0.0034 0.0
ACF 0.1325 0.013 0.098 0.152 0.234 0.332 0.495 0.833 0.3449
MW 36.01 16.04 30.07 44.10 67.28 110.9 170.9 282.1 18
SHIFT 0 0 0 0 0 0 0 0 0.25
BIC 0.036
BIC 0.05 0
BIC 0.08 0 0
BIC 0.1002 0.09281 0 0
BIC 0.1 0 0.00385 0.00385 0
BIC 0.1 0 0.00630 0.00630 0 0
BIC 0.1 0.1392 0.00600 0.00600 0 0 0
BIC 0 0 0 0.0 0 0 0 0
END
Notes:
The usual parameters required for each equation of state component must also be suppled for a water component.
Although this component is termed H2O, the Søreide-Whitson equation does account for salinity as specified with the BRINE keyword.
Following table 3 in Søreide and Whitson, however, we specify pure water component properties in
EOS COMPand allow the equation of state to do the salinity correction.When using
SWEOS, the last component must be called H2O, if not an error will be thrown.The aqueous phase viscosity and enthalpy values in the
EOS3Pmode with the Søreide-Whitson equation are obtained from the salinity-dependent brine correlations built in to the simulator, rather than being obtained from the Lorentz-Bray-Clark compositional correlation or the equation of state deviation factor applied to the ideal gas heat capacity. These are generally more accurate.Although a full set of binary interaction coefficients should be entered with the
BICsub-keyword of theEOS COMPblock, the binaries between the water component and the non-water components (the last line of BIC values) will be overwritten internally by the Søreide-Whitson values.The Søreide-Whitson equation predictions will be used for the molar and the mass densities of the brine. Note that this will generally need some setting of the water component
SHIFTvalues to tune the aqueous phase density.
Equlibration and initialisation
There is no need to set up binary interaction coefficients between the non- H2O and H2O phases: these will be set automatically by the equation of state.
If setting up a composition with respect to depth table with ZMFVD, this can be done in the same way as for the non- SWEOS case.
If using ZMF to specify a single initial composition for the study, leave the last (H2O) mole fraction at zero.
There is no need to include the H2O mole fraction in ZMF and ZMFVD: the water transition zone will be created as a function of capillary pressure in the normal way and then total sytem mole fractions created internally.
Separator modelling
When produced fluids are run though the separators, the water component is still reported separately as a surface water rate.
The remaining components are split into stock tank oil and tock tank gas.