Application of Electrokinetics for Enhanced Oil Recovery - Electrokinetics for Petroleum and Environmental Engineers - page 126

Surface change

Net negative

Matrix grain

Bound layer

HC

HC

HC

Pore Throat
Electro-Osmotic

HC

HC

HC

HC HC

HC

Matrix grain

EXPLANATION

H 2 O molecule
Hydrocarbon

Cl -

Bound layer

Na +

Figure 3.14 Pore throat schematic showing electrokinetic transport of the outer
Helmholtz layer, modifying the effective pore throat size for fluid flow (after Hill, 1999)

1997,1997, Tchillingarian, 1952) showed up to forty-fold volumetric
fluid flow increases in cores containing clays, compared to only 2 - 3 fold
increases in pure silica cores, as shown in figure 3.15. Chilingar, et. al. (1970)
speculated that this latter (silica core) fluid flow might be due to a thermal
effect. Mitchell (1993) maintained that all silica minerals show increased
flow, under DC fields, but that those with high cation exchange capacity
(CEC) exhibit the greatest flow increases. The results in figure 3.15 agree
with Mitchell's (1993) argument.
For those pore throats completely filled with the Helmholtz double layer,
the application of current will develop salinity gradients across the cation
selective membranes, which will store energy. Any fluctuation in the local
electric fields will result in discharge of this stored energy, similar to dis-
charging a super capacitor (Conway, 1999), potentially inducing a break-
down of complex hydrocarbon molecules, resulting in simpler daughter
product molecules.

3.9 DCEOR Field Operations

Figure 3.16 illustrates one possible DCEOR field implementation, where
anode(s) are placed near the ground surface and cathode(s) are placed
in, or near, producing well(s). An alternative configuration utilizes both