Reduction of Contaminants in Soil and Water By Direct Electric Current - Electrokinetics for Petroleum and Environmental Engineers - page 86

Table 2.3 Physical properties of the formation oil and surrogate water (Kentucky
field)

Fluid Properties

Natural formation
oil

API 22; Dynamic viscosity = 66.5 cP
Specific gravity =0.92 at 20°C

Electrolyte
solution
(Surrogate forma-
tion water)

Salinity= 33,000 ppm; Electrical conductivity = 45,000 μS
pH = 7.50; Major elements: Na, Cl, Mg, S, K, Ca, Br

the cores. The oil recovery results suggest a direct relation between the ini-
tial oil content of the formation and the measured oil recovery. Modeling
studies on two-phase EO flow revealed that the drag force exerted by the
mobile water phase on the oil phase increases with water saturation of the
pore up to about 50%. The oil production decrease when water saturation
is above 50% and oil saturation drops below 50% (Ghazanfari et al. 2013b).
The higher recovery of oil with higher initial oil/water ratio is attributed to
the availability of more oil.
In a separate set of experiments, sandstone core specimens retrieved
from a deep oil formation in Pennsylvania were used in the experiments
to assess oil recovery, permeability change, and effect of the magnitude
of current density on oil extraction. Unlike the Kentucky cores discussed
above, the Pennsylvania cores had very low initial oil content. In order to
better control the oil and water saturation, these cores were impregnated
with Pennsylvania oil (API 47; Dynamic viscosity = 38.7 cP) and surrogate
formation water (i.e., with the same properties as presented in Tables 2.2)
prior to testing. First, the cores were dried and vacuumed. Then, oil and
water were injected into the cores using a high-pressure injection pump
(Quizix Pump) to attain the desired initial oil-water saturations. Once sat-
urated, the cores were tested under a constant current density of 1 Amp/m 2
for 130 hours. The physical properties of the four Pennsylvania cores used
in these experiments are given in Table 2.4.
As presented in table 2.4, most of the oil was produced at the catholyte
and the oil recovered at the anolyte was negligible. The total oil recovered
was in the range of 0.5 to 6% by mass of the initial oil content of the cores.
Similar to the Kentucky cores, the highest oil recovery corresponded to
core PA3, which had the highest initial oil content and highest hydraulic
permeability.