Reduction of Contaminants in Soil and Water By Direct Electric Current - Electrokinetics for Petroleum and Environmental Engineers - page 83

and without the GS caps, respectively. The sample containing the GS caps
showed larger concentrations of Pb(II) accumulated in the caps, and
very little of the element passed into the electrode chambers. Overall, the
results showed that in samples tested without the GS caps more of the
Pb(II) remained in the soil; while, the samples containing the caps showed
lesser concentrations of Pb(II) in the soil with larger concentrations in the
areas of the GS caps for the same duration of electrokinetic treatment. The
larger removal of the lead into the GS caps, particularly on the cathode
side is attributed to continued flow of higher current and electro-osmotic
advection, whereas precipitation of lead at the cathode interface of the soil
without the caps inhibited the current and electro-osmotic flow hinder-
ing the Pb(II) transport overall. Indeed, the steady low current measured
with caps was 3 times larger than the one without the caps. The sorptive
capacity of the cathode cap would have kept the Pb(II) and its hydroxide
precipitates on the solid surfaces without causing blockage in the porous
matrix. These results indicate that application of site and contaminant
specific containment packs can work synergistically with EK remediation
when the goal is to collect the contaminant in a small volume of substrate
from where it can be recovered, while regenerating the substrate for fur-
ther use.

2.4 Transport and Extraction of Crude Oil

2.4.1 Laboratory Evidence of Oil Extraction

Chilingar and co-workers investigated the use of electrokinetics to
augment reservoir energy during petroleum production (Amba et al.
1964,1965; Chilingar et al., 1968a,b). They found that application of direct
electric current resulted in several fold increase in the flow rate of oil and
water (i.,e., as much as 34 fold) in both synthetic and natural sandstone
cores. Synthetic cores were prepared using various percentages of different
types of clay admixed with 200 mesh size silica or CaCO 3 powder. Also, it
was found that the effective permeability to kerosene of core samples con-
taining connate water (i.e., entrapped water in the pores when the rocks
were formed) was increased by 50 percent on temporary application of
direct potential gradient.
Successful field pilot tests have been reported on the application of EEOR
(Electrically Enhanced Oil Recovery) in heavy oil fields in the Santa Maria
(California) basin and the Eastern Alberta Plains (Wittle et al., 2007, 2008).
In these pilot tests, the EEOR was found to be more efficient than other