Giving the physics a chance: how to reduce the impact of numerical errors

  • Date: 03/07/2008

Margot Gerritsen, Department of Energy Resources Engineering, Stanford University


Simon Fraser University


Numerical errors are generally a bother, but in the case of adverse
mobility ratio flows, such as those encountered when injecting water or
gas (CO2) in oil reservoirs, they can be a real nuisance. In this talk
we discuss the well-known grid orientation effect, which causes
solutions to be very different depending on the orientation of the grid
with respect to the general flow direction. It is not possible to
completely remove this effect without introducing unacceptable levels
of numerical damping. However, careful analysis of numerical errors in
some popular discretization methods for the governing transport
equations gave us two ideas to reduce their impact. The first is a
correction of the solution in the critical near-well region, which can
be applied to any discretization and gridding method. The second idea
amounts to augmentation of existing schemes to render the numerical
error that causes most problems isotropic.