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HYDRATE

Defines options for the Hydrate subsurface flow mode. For more details and governing equations see the Theory Guide.

SIMULATION Options

TIMESTEPPER Options

NEWTON_SOLVER Options

HYDRATE Block

Examples

SIMULATION Options

(under SUBSURFACE_FLOW in SIMULATION PROCESS_MODELS block)

Basic Settings

ARITHMETIC_GAS_DIFFUSIVE_DENSITY

Use arithmetic weighting for gas diffusivity.

GAS_COMPONENT_FORMULA_WEIGHT <float>

Specifies the molecular weight of the gas component [g/mol].

HARMONIC_GAS_DIFFUSIVE_DENSITY

Use harmonic weighting for gas diffusivity.

IMMISCIBLE

Disables solubility calculations.

LIQUID_COMPONENT_FORMULA_WEIGHT <float>

Specifies the molecular weight of the liquid component [g/mol].

LOGGING_VERBOSITY <integer>

Prints additional convergence logging to the screen when the integer is greater than 0 (for process models that have logging verbosity implemented).

NO_STATE_TRANSITION_OUTPUT

Eliminates “State Transition” screen output. E.g. State Transition: 2 Phase -> Gas at Cell 23331

NO_TEMP_DEPENDENT_DIFFUSION

Turns off temperature-dependent diffusion coefficients.

NUMBER_OF_EQUATIONS <int>

Specifies the number of equations solved (3: air/water/energy (default), 4: air/water/solute/energy)

REPLACE_INIT_PARAMS_ON_RESTART

Forces the overwrite of base (0) porosity and permeabilities off which solution dependent parameters may be calculated.

REVERT_PARAMETERS_ON_RESTART

Reverts permeability and porosity back to the values specified in the input file instead of the checkpointed values.

SKIP_RESTART

On a restarted simulation, employs the initial condition for process model instead of the restarted solution.

SOLUBLE_MATRIX

Allows the rock matrix to dissolve with changing solubility conditions. Requires NUMBER_OF_EQUATIONS 4 and SOLUTE SALT.

SOLUTE <string>

Specifies the solute used when NUMBER_OF_EQUATIONS 4. Default SALT.

Expert Settings

CHECK_MAX_DPL_LIQ_STATE_ONLY

When calculating the maximum change in liquid pressure over a time step, consider only liquid state cells. Helpful when capillary pressures are extreme.

COUNT_UPWIND_DIRECTION_FLIP

Turns on and increments a counter whenever the upwind direction changes. This is only useful for non-parallel execution.

DIFFUSE_XMASS

Calculate gradietns of dissolved gas in diffusion equation based on mass fraction instead of mole fraction.

FIX_UPWIND_DIRECTION

Limits the update of the upwind direction (based on pressure gradients) to UPWIND_DIR_UPDATE_FREQUENCY Newton iterations.

PHASE_CHANGE_EPSILON <float>

Assign a fixed initial saturation of a new phase that is created upon a state change.

RESTRICT_STATE_CHANGE

Restricts any changes of state to only occur once per Newton iteration.

TWO_PHASE_STATE_ENERGY_DOF <string>

Sets the primary dependent variable for the energy conservation equation for cells in a two-phsae state (3rd dof) [TEMPERATURE, AIR_PRESSURE]. (default = TEMPERATURE, which is most tested)

UNFIX_UPWIND_DIRECTION

Turns off fixing of upwind direction.

UPWIND_DIR_UPDATE_FREQUENCY

Frequency at which the upwind direction is updated if FIX_UPWIND_DIRECTION is included.

WINDOW_EPSILON <float>

Specifies the tolerance or window that must be exceeded before state change will occur.

LEGACY_FLUXES

Use fluxes from an earlier version of HYDRATE mode, similar to GENERAL mode flux formulation. Default is to use fluxes similar to SCO2 mode.

TIMESTEPPER Options

Basic Settings

CFL_GOVERNOR

Specifies a maximum CFL (Courant–Friedrichs–Lewy) number that governs time step size. Subsequent time steps are calculated as a function of the maximum flow velocity and grid discretization such that the CFL is not exceeded.

CONCENTRATION_CHANGE_GOVERNOR

Specifies a maximum absolute change in concentration [mole fraction] that governs time step size. Subsequent time steps are calculated such that the governing concentration change is not exceeded.

PRESSURE_CHANGE_GOVERNOR

Specifies a maximum absolute change in pressure [Pa] that governs time step size. Subsequent time steps are calculated such that the governing pressure change is not exceeded.

SATURATION_CHANGE_GOVERNOR

Specifies a maximum absolute change in saturation [-] that governs time step size. Subsequent time steps are calculated such that the governing saturation change is not exceeded.

TEMPERATURE_CHANGE_GOVERNOR

Specifies a maximum absolute change in temperature [C] that governs time step size. Subsequent time steps are calculated such that the governing temperature change is not exceeded.

NEWTON_SOLVER Options

Basic Settings

ANALYTICAL_JACOBIAN

Calculate derivatives in Jacobian analytically.

ATOL <float>

Declare convergence when the 2-norm of residual is less than ATOL \(\left(\|f(x_n)\|<\text{ATOL}\right)\). (default: \(10^{-50}\)).

CENTRAL_DIFFERENCE_JACOBIAN

Uses a central difference formulation when calculating the entries in the Jacobian. Default is a forward difference.

CONVERGENCE_INFO

Opens a block for toggling ON/OFF convergence information in screen output (default: YES to all). See example below.

  • 2R, FNORM, 2NORMR - 2-norm of residual

  • 2X, XNORM, 2NORMX - 2-norm of solution

  • 2U, UNORM, 2NORMU - 2-norm of update

  • IR, INORMR - inifinity norm of residual

  • IU, INORMU - inifinity norm of update

DTOL <float>

Declare divergence (cut the time step) when the 2-norm of the residual is greater than DTOL times the 2-norm of the initial residual \(\left(\frac{\|f(x_n)\|}{\|f(x_0)\|}>\text{DTOL}\right)\). (default: \(10^{4}\)).

HYDRATE_UPDATE_INF_TOL

Needs definition

MAXIMUM_NUMBER_OF_ITERATIONS <int>

Maximum number of Newton iterations before reporting failed convergence.

NO_PRINT_CONVERGENCE

Toggle off printing of convergence information.

NTRDC_OPTIONS or NTR_OPTIONS

Opens a block for trust-region options and parameters (SNES_TYPE NTRDC or SNES_TYPE NTR required)

  • TR_TOL - trust-region tolerance (default: \(1.0^{-12}\))

  • ETA1 - trust-region parameter \(0.0 \le \eta_1 \le \eta_2\), \(\density \ge \eta_1\) breaks out of the inner iteration (default: \(\eta_1=0.001\))

  • ETA2 - trust-region parameter \(0.0 \le \eta_1 \le \eta_2\), \(\density \ge \eta_2\) shrinks the trust-region (default: \(\eta_2=0.25\))

  • ETA3 - trust-region parameter \(\eta_3 > \eta_2\), \(\density \ge \eta_3\) expands the trust-region (default: \(\eta_3=0.75\))

  • T1 - trust-region parameter, shrinking factor of trust-region (default: 0.25)

  • T2 - trust-region parameter, initial size of trust-region, \(\Delta_0*\|x\|_2\) (default: 0.1)

  • DELTA_M - trust-region parameter, max size of trust-region, \(\Delta_M*\|x\|_2\) (default: 0.5)

  • DELTA_0 - trust-region parameter, initial size of trust-region, \(\Delta_0*\|x\|_2\) (default: 0.1)

  • AUTO_SCALE - TRUE enables solution update scaling meaning all types of unknowns are equally treated when evaluating solution update (recommended for WIPP-FLOW, TH); FALSE disables solution update scaling meaning that solution update evaluation will focus more on pressure than other unknowns (recommended for GENERAL, HYDRATE).

  • AUTO_SCALE_MAX - used with AUTO_SCALE, caps the maximum auto-scaling factor

NUMERICAL_JACOBIAN

Calculate derivatives in Jacobian numerically.

PRINT_LINEAR_ITERATIONS

Prints the number of linear iterations for each Newton iteration to the screen.

RTOL <float>

Declare convergence when the 2-norm of the residual is less than RTOL times the 2-norm of the initial residual \(\left(\frac{\|f(x_n)\|}{\|f(x_0)\|}<\text{RTOL}\right)\). (default: \(10^{-8}\)).

SNES_TYPE <string>

The default is LINE_SEARCH (Basic, see PETSc documenetation) from PETSc which is Newton-Raphson nonlinear solver. NTRDC is the Newton Trust-Region Dogleg-Cauchy nonlinear solver, and NTR is the Newton Trust-Region nonlinear solver. The difference between NTRDC and NTR is that NTRDC adds steepest-descent solution update to the Newton solution iff it optimizes better than Newton solution alone within the trust-region. NTR only applies Newton solution update and it is truncated by the trust-region. NTRDC MAY perform better with LESS phase state change simulations for GENERAL MODE.

STOL <float>

Declare convergence when the 2-norm of the update divided by the 2-norm of the solution is less than STOL \(\left(\frac{\|x_n-x_{n-1}\|}{\|x_{n-1}\|}<\text{STOL}\right)\). (default: \(10^{-8}\)).

VERBOSE_LOGGING

Prints additional convergence information to screen.

Expert Settings

ABS_UPDATE_INF_TOL <float>

Specify a single infinity norm convergence tolerance on the absolute value of all solution updates.

AIR_PRES_ABS_UPDATE_INF_TOL <float>

Specify a maximum absolute change in air partial pressure in the gas phase.

AIR_PRES_REL_UPDATE_INF_TOL <float>

Specify a maximum relative change in air pressure.

DAMPING_FACTOR <float>

The scalar value by which the solution is damped between each Newton-Raphson iteration. Acceptable values on (0,1].

ENERGY_RESIDUAL_ABS_INF_TOL

Specify the infinity norm convergence tolerance on the absolute residual of energy. (default = 1e-5)

ENERGY_RESIDUAL_SCALED_INF_TOL <float>

Specify the infinity norm convergence tolerance on the scaled residual of energy.

GAS_PRES_ABS_UPDATE_INF_TOL <float>

Specify a maximum absolute change in gas phase pressure.

GAS_PRES_REL_UPDATE_INF_TOL <float>

Specify a maximum relative change in gas phase pressure.

GAS_RESIDUAL_ABS_INF_TOL

Specify the infinity norm convergence tolerance on the absolute residual of gas mass (gas phase). (default = 1e-5)

GAS_RESIDUAL_SCALED_INF_TOL <float>

Specify the infinity norm convergence tolerance on the scaled residual of gas mass (gas phase primary component).

LIQUID_PRES_ABS_UPDATE_INF_TOL <float>

Specify a maximum absolute change in liquid phase pressure.

LIQUID_PRES_REL_UPDATE_INF_TOL <float>

Specify a maximum relative change in liquid phase pressure.

LIQUID_RESIDUAL_ABS_INF_TOL

Specify the infinity norm convergence tolerance on the absolute residual of water mass (liquid phase). (default = 1e-5)

LIQUID_RESIDUAL_SCALED_INF_TOL <float>

Specify the infinity norm convergence tolerance on the scaled residual of water mass (liquid phase).

MATRIX_TYPE <string>

Format of main solver matrix. PETSc Mat (i.e. AIJ, BAIJ, or HYPRESTRUCT).

MAXF <int>

Maximum number of function evaluations before reporting failed convergence.

MAXIMUM_PRESSURE_CHANGE <float>

The change in pressure is truncated to within this limit.

MAX_ITERATION_BEFORE_DAMPING <integer>

Specifies the threshold number of Newton iterations before damping is imposed.

MAX_NORM <float>

Declare divergence (cut the time step) when the infinity norm of the residual is greater than MAX_NORM \(\left( \| f(x_n) \|_{inf} > \text{MAX_NORM} \right)\). (default: \(10^{20}\)).

MINIMUM_NUMBER_OF_ITERATIONS <int>

Newton solver convergence requires at least MINIMUM_NUMBER_OF_ITERATIONS.

NO_FORCE_ITERATION

Toggle off the forcing of at least 1 linear iteration. The default is to force at least 1 linear iteration. In a quasi-stationary state, the initial residual may be sufficiently small for convergence, but often it is better to force at least one iteration.

NO_INFINITY_NORM

Toggle off calculation of infinity norm on residual and update vectors. The default is to calculate the infinity norm.

PRECONDITIONER_MATRIX_TYPE <string >

Format of preconditioning matrix. PETSc Mat (i.e. AIJ, BAIJ, or HYPRESTRUCT). Default is same as solver.

PRES_ABS_UPDATE_INF_TOL <float>

Specify a single maximum absolute change in liquid phase, gas phase, and air partial pressure. (default = 1)

PRES_REL_UPDATE_INF_TOL <float>

Specify a single maximum relative change in liquid phase, gas phase, and air partial pressure. (default = 1e-3)

PRINT_DETAILED_CONVERGENCE

Toggle on printing of detailed convergence information.

REL_UPDATE_INF_TOL <float>

Specify a single infinity norm convergence tolerance on the relative solution update.

RESIDUAL_ABS_INF_TOL

Specify a single infinity norm convergence tolerance on all absolute residuals. (default = 1e-5)

RESIDUAL_INF_TOL

Specify a single infinity norm convergence tolerance on all absolute and scaled residuals. (default = 1e-5, abs; 1e-6, scaled)

RESIDUAL_SCALED_INF_TOL <float>

Specify a single infinity norm convergence tolerance on all scaled residuals. (default = 1e-6)

SAT_ABS_UPDATE_INF_TOL <float>

Specify a maximum absolute change in phase saturation. (default = 1e-5)

SAT_REL_UPDATE_INF_TOL <float>

Specify a maximum relative change in phase saturation. (default = 1e-3)

TEMP_ABS_UPDATE_INF_TOL <float>

Specify a maximum absolute change in temperature. (default = 1e-5)

TEMP_REL_UPDATE_INF_TOL <float>

Specify a maximum relative change in temperature. (default = 1e-3)

UPDATE_INF_TOL <float>

Specify a single infinity norm convergence tolerance on the absolute and relative updates of all solution updates.

XMOL_ABS_UPDATE_INF_TOL <float>

Specity a maximum absolute change in mass fraction of dissolved gas in the aqueous phase. (default = 1e-9)

XMOL_REL_UPDATE_INF_TOL <float>

Specify a maximum relative change in mass fraction of dissolved gas in the aqueous phase over a given timestep. (default = 1e-3)

HYDRATE Block

(within SUBSURFACE block)

GAS <string>
CO2

Use CO2 as the working gas

CH4

Use CH4 as the working gas (default)

AIR

Use air (non hydrate-forming gas) as the working gas.

METHANOGENESIS
Invokes a methanogenesis source term. Current source implementation (following Malinverno, 2010) requires:
NAME <string>

Arbitrary name of the methanogenesis source

ALPHA <float>

Seafloor labile organic carbon [wt%]

LAMBDA <float>

Methanogenesis reaction rate [1/s]

V_SED <float>

Sedimentation rate [m/s]

SMT_DEPTH <float>

Depth to the sulfate-methane transition [m]

K_ALPHA <float>

Conversion factor from organic carbon to methane (typically 2241)

WITH_SEDIMENTATION

Turns on sedimentation. Moves immobile pore species at the sedimentation rate specified in the METHANOGENESIS block and in the direction of gravity.

WITH_GIBBS_THOMSON

Turns on the Gibbs-Thomson effect. Shifts the gas hydrate phase boundary as a function of required subcooling to precipitate hydrate.

GT_3PHASE

Applies the Gibbs-Thomson effect in 3-phase and 4-phase states.

ADJUST_SOLUBILITY_WITHIN_GHSZ

Applies a correction to methane solubility within the hydrate stability zone as a function of distance from the phase boundary.

NO_PC

Turns off capillary pressure.

NO_EFFECTIVE_SATURATION_SCALING

Turns off scaling of saturations of mobile pore species by the total amount of mobile pore fluids.

NO_ICE_VOLUME_CHANGE

Turn off volume change due to ice freezing.

NO_SOLID_SATURATION_PERM_SCALING

Turns off absolute permeability scaling by hydrate saturation.

PERM_SCALING_FUNCTION <string>

Selects the specific function used for absolute permeability scaling as a function of hydrate saturation. Current options: DAI_AND_SEOL

HYDRATE_PHASE_BOUNDARY <string>

Sets the gas hydrate phase boundary equation for CH4-hydrate. Default is Kamath, 1984. Current options: MORIDIS, MORIDIS_SIMPLE

HENRYS_CONSTANT <string>

Set function for Henry’s constant for methane. Current default: Carroll and Mather, 1997. Current options: CRAMER

SALINITY <float>

Set a constant salinity, which shifts the hydrate phase boundary and the freezing point of water.

THERMAL_CONDUCTIVITY <string>

Set the thermal conductivity model. Default is a phase saturation weighted average. Current options: IGHCC2

BC_REFERENCE_PRESSURE

Reference pressure for seepage boundary condition.

Examples

SIMULATION
  SIMULATION_TYPE SUBSURFACE
  PROCESS_MODELS
    SUBSURFACE_FLOW flow
      MODE HYDRATE
    /
  /
END
...
SUBSURFACE
  NUMERICAL_METHODS FLOW
    NEWTON_SOLVER
      USE_INFINITY_NORM_CONVERGENCE
    /
  /
  ...
  HYDRATE
    GAS CH4
    PERM_SCALING_FUNCTION DAI_AND_SEOL
    WITH_GIBBS_THOMSON
    GT_3PHASE
    ADJUST_SOLUBILITY_WITHIN_GHSZ
    WITH_SEDIMENTATION
    METHANOGENESIS
     NAME ss_methanogenesis
     ALPHA 0.005
     K_ALPHA 2241
     LAMBDA 1.d-14
     V_SED 3.17d-11
     SMT_DEPTH 10.d0
    /
  /
  ...