dimensional fluid and thermal transport. SUTRA simulates the fluid flow and the pore
pressure changes with time. Once the pore pressures were calculated in SUTRA they
were transferred back into the prism-growth/flow model, which calculates effective
stress, porosity, and permeability before beginning the next loading step.
During hydrofracture, the model checks for regions that have reached the criteria
for vertical hydrofracture after every seaward advancement of the prism. If pressures
meet the vertical hydrofracture criteria, then the model increases vertical permeability
from the point of lithostatic pressure up to the decollement. If pressures are less than the
assigned criteria for hydrofracture the permeability values are assigned according to
permeability-porosity relationship.
SUTRA uses a backwards finite-difference scheme which enhances numerical
stability. The large permeability contrast during the introduction of hydrofractures into
the model was challenging for the iterative solver, especially for the thermal transport
simulations. However, by reducing the contrast between the highest and the lowest
permeabilities and increasing upstream weighting for the transport, convergence was
obtained.
Model Equations
Combining the mass conservation of fluid with Darcy's law, the following equation
can be written for two-dimensional transient flow:
K h K a'h Sh
K X X K2 a Q2 --d (1)
where Ss is specific storage [L-1], h is hydraulic head [L], x and y are spatial
coordinates, Q is a source term reflecting processes such as loading that affect fluid
volume or pressure [T-1]. The left hand side term accounts for fluid flow into and out of a