ROCKS

ROCKS introduces material parameters for different reservoir domains.

Record ROCKS.1

Free Format for 9 parameters, or Format (A5, I5, 7E10.4)

MAT, NAD, DROK, POR, (PER (I), I = 1,3), CWET, SPHT

MAT material name (rock type). In wellbore simulation, the rock name for the wellbore cell must start with the letter “w” or “x”, where “w” indicates normal (open) wellbore cell whereas “x” indicates the wellbore cells filled with porous medium;

NAD if zero or negative, defaults will take effect for a number of parameters (see below);

≥1: will read another data record to override defaults.

≥2: will read two more records with domain-specific parameters for relative permeability and capillary pressure functions.

DROK rock grain density (kg/m3). If DROK is set to a very large value (typically 1.0E50), a constant temperature boundary condition can be specified (but variable pressure/saturation).

POR default porosity (void fraction) for all elements belonging to domain “MAT" for which no other porosity has been specified in block INCON.

PER(I) I = 1,3 absolute permeabilities along the three principal axes, as specified by ISOT in block CONNE.

CWET formation heat conductivity under fully liquid-saturated conditions (W/m ˚C).

SPHT rock grain specific heat (J/kg ˚C). Domains with SPHT > $10^4$J/kg ˚C will not be included in global material balances. This provision is useful for boundary nodes, which are given very large volumes so that their thermo-dynamic state remains constant. Because of the large volume, inclusion of such nodes in global material balances would make the balances useless.

Some specific rock names may have special meanings. When a (dummy) domain named “SEED” is specified, the absolute permeabilities specified in PER(I) are modified by the block-by-block permeability modifiers (PM) according to

$k_n\rarr k_n'=k_n*\zeta_n$ (8-5)

Here, $\kappa_n$ is the absolute (“reference”) permeability of grid block n, as specified in data block ROCKS for the domain to which that grid block belongs, is the modified permeability, and $\zeta_n$ is the PM coefficient. When PM is in effect, the strength of capillary pressure will be automatically scaled according to (Leverett, 1941)

$P_{cap,n}\rarr P_{cap,n}'=P_{cap,n}/\sqrt{\zeta_n}$ (8-6)

No grid blocks should be assigned to this domain; the presence of domain ‘SEED’ simply serves as a flag to put permeability modification into effect. Random (spatially uncorrelated) PM data can be internally generated in TOUGH4. Alternatively, externally defined permeability modifiers may be provided as part of the geometry data (PMX) in block ELEME. Available PM options are:

(1) externally supplied : $\zeta_n=PMX-PER(2)$

(2) “linear” : $\zeta_n=PER(1)\times s-PER(2)$

(3) “logarithmic” : $\zeta_n=e^{-PER(1)\times s}-PER(2)$

where s is a random number between 0 and 1

Data provided in domain ‘SEED’ are used to select the following options.

DROK random number seed for internal generation of "linear" permeability modifiers.

= 0: (default) no internal generation of "linear" permeability modifiers.

> 0: perform "linear" permeability modification; random modifiers are generated internally with DROK as seed.

POR random number seed for internal generation of "logarithmic" permeability modifiers

= 0: (default) no internal generation of "logarithmic" permeability modifiers.

> 0: perform "logarithmic" permeability modification; random modifiers are generated internally with POR as seed.

Note if both DROK and POR are specified as non-zero, DROK takes precedence. And if both DROK and POR are zero, permeability modifiers as supplied through ELEME data will be used.

PER(1) scale factor (optional) for internally generated permeability modifiers.

= 0: (defaults to PER(1) = 1): permeability modifiers are generated as random numbers in the interval (0, 1).

> 0: permeability modifiers are generated as random numbers in the interval (0, PER(1)).

PER(2) shift (optional) for internal or external permeability modifiers.

= 0: (default) no shift is applied to permeability modifiers.

> 0: permeability modifiers are shifted according to = – PER(2). All < 0 are set equal to zero.

Note that the domain ‘SEED’ is not required in TOUGH4 if externally defined permeability modifiers in block ELEME are used without any shift.

Other specific rock names:

(1) “REFCO”, input density, viscosity and compressibility at the reference pressure, temperature at data lot 5, 6, 7, 3, and 4, respectively. This is used by EOS9 only.

(2) “GEOTH”, input reference elevation, temperature, and geothermal gradient at data lot 5, 6, and 7. This is used for wellbore simulation only.

(3) “QLOSS”, input parameters for analytical solution of radial heat exchange between fluids in a wellbore and the surrounding formation for option MOP(15)=5. Details of the parameters for input can be found at the discussion for MOP(15) input. The initial temperature of surrounding rock can be provided through POR in record ROCKS.1.

Record ROCKS.1.1 (optional, NAD ≥ 1 only)

Free format for 10 parameters, or Format (10E10.4)

COM, EXPAN, CDRY, TORTX, GK, XKD1-XKD5 (FOCM)

COM pore compressibility (Pa-1), $(1/\phi)(\partial \phi/\partial P)_T$ (default is 0).

EXPAN pore expansivity (1/ ˚C), $(1/\phi)(\partial \phi/\partial P)_P$ (default is 0).

CDRY formation heat conductivity under desaturated conditions (W/m ˚C), (default is CWET).

TORTX tortuosity factor for binary diffusion. If TORTX = 0, a porosity and saturation-dependent tortuosity will be calculated internally from the Millington and Quirk (1961) model, Eq. (4-11). When diffusivities, FDDIAG in data block DIFFU, are specified as negative numbers, $\tau_0\tau_\beta=S_\beta$will be used.

GK Klinkenberg parameter b ( $Pa^{-1}$) for enhancing gas phase permeability according to the relationship kgas = k * (1 + b/P).

XKD1-5 Distribution coefficients for as more as 5 tracers in current rock, in the aqueous phase, $m^3kg^{-1}$. Distribution coefficients can also be inputted through key word “TRACR” for specific tracer.

FOCM fraction of organic carbon present in domain; used for calculating amount of VOC adsorbed. FOCM is used only in TMVOC. FOCM shares the same input data lot with XKD1. This conflict may be avoided through IE(25), see Appendix C. The purpose of remaining this option is to maintain the compatibility of input file for TMVOC and other modules from TOUGH3.

Record ROCKS.1.2 (optional, NAD ≥ 2 only)

Free format for 11 parameters, or Format (I5, 5X,7E10.4)

IRP, (RP(I), I= 1,10)

IRP integer parameter to choose type of relative permeability function (see Appendix A).

RP(I) I = 1, ..., 10 (use free format) or 7 (use formatted input) parameters for relative permeability function (Appendix A).

Record ROCKS.1.2.1 (optional, IRP = 12 or 41, use the formatted input only)

Format (3E10.4)

RP(I), I= 8,10

RP(I) I = 8, ..., 10 parameters for relative permeability function (Appendix A).

Record ROCKS.1.3 (optional, NAD ≥ 2 only)

Free format for 14 parameters, or Format (I5, 5X,7E10.4)

ICP, (CP(I), I = 1,13)

ICP integer parameter to choose type of capillary pressure function (see Appendix B).

CP(I) I = 1, ..., 13 (for free format) or 7 (for formatted input) parameters for capillary pressure function (Appendix B).

Record ROCKS.1.3.1 (optional, ICP = 12 or 41, formatted input only)

Format (6E10.4)

CP(I), I = 8,13

CP(I) I = 8, ..., 13 parameters for capillary pressure function (Appendix B).

Record ROCKS.1.4 (optional, IRP=40 and ICP=40 only)

Free format for 1 parameter

Num_Sg

Num_Sg The total number of gas saturations (rows) for the input table of relative permeability and capillary pressure.

Record ROCKS.1.4.1 (optional, Num_Sg>0 only)

Free format for 4 parameters, or Format (4E10.4)

Sg, kg, kw, pc

sg gas saturation.

kg relative permeability in gas phases corresponding to gas saturation sg.

kw relative permeability in aqueous phases corresponding to gas saturation sg.

pc capillary pressure corresponding to gas saturation sg.

Repeat record 1.4.1 for Num_Sg times.

Repeat records 1, 1.1, 1.2, 1.2.1., 1.3, 1.3.1, 1.4, and 1.4.1 for different reservoir domains.

Record ROCKS.2 A blank record closes the ROCKS data block.

Used in: All EOS modules

Example:

ROCKS

SANDY, 2, 2500., 1.e-4, 1.e-12*3, 2.5 ,1000. //ROCKS.1

1.e-8, , , 0.25 //ROCKS.1.1

1, 0., 0., 1., 1., //ROCKS.1.2

8 //ROCKS.1.3