Here we list the defaults that the RESERVOIR_DEFAULTS keyword imposes on each input card, unless overridden. For more information see each respective card and keyword.
ANALYTICAL_JACOBIAN: this is automatically selected. Analytical Jacobian increases the accuracy and convergence of the nonlinear solver. The opposite is NUMERICAL_JACOBIAN, whichuses numerical differences to find the Jacobian and is usually less accurate.
MAX_PRESSURE_CHANGE: this is set to 5.5d6 Pa. This value has been observed to provide a good balance of safety and timestep acceleration for reservoir models under test.
Card: TIMESTEPPER FLOW.
TS_ACCELERATION: this is set to 100. This value has been observed to provide a good balance of safety and timestep acceleration for reservoir models under test.
PC_TYPE: this is set to CPR, the constrained pressure residual, a multigrid based preconditioner. CPR is generally required for most difficult reservoir models.
KSP_TYPE: this is set to FGMRES, the flexible gmres linear solver is a common solver and works well with the CPR preconditioner.
GMRES_MODIFIED_GRAMSCHMIDT: this is automatically selected. A reliable setting for FGMRES for our purposes.
GMRES_RESTART: this is set to 100. A reliable setting for FGMRES for our purposes.
MAXIT: this is set to 80. Higher than this indicates the linear solver would benefit more from a timestep cut than more iterations.
STOL: set to 1.0D-16. STOL is not often a reliable convergence measure so in most cases a step should converge by some other criterion.
MAXIT: set to 15. A healthy Newton convergence is usually up to about 10 iterations. More than this and it is often inefficient to force it to converge at the given timestep length.
ITOL: set to 1.0D-8. A reliable absolute convergence tolerance. Works well with the RTOL default already in place.
ITOL_S: set to 1.0D-8. Also the computation of scaled norms is activated.