WorldOil

Simulations reveal mechanisms of seismic waves for EOR

Seismic stimulation aims to enhance oil production by sending seismic waves across a reservoir to liberate immobile patches of oil. For seismic amplitudes above a well-defined (analytically expressed) dimensionless criterion, the force perturbation associated with the waves can indeed liberate oil trapped on capillary barriers and get it flowing again under the background pressure gradient. Subsequent coalescence of the freed oil droplets acts to further enhance oil movement because longer bubbles more efficiently overcome capillary barriers than do shorter bubbles. Poroelasticity theory defines the effective force that a seismic wave adds to the background fluid-pressure gradient, while the lattice-Boltzmann model in two dimensions is used to perform the pore-scale numerical simulations. The dimensionless numbers (groups of material and force parameters) involved in seismic stimulation are carefully defined so that the numerical simulations can be applied to field-scale conditions. Using the analytical criteria defined by the authors,* there is a significant range of reservoir conditions over which seismic stimulation can be expected to enhance oil production.