EEOR in Carbonate Reservoirs - Electrokinetics for Petroleum and Environmental Engineers - page 169

further enhanced at temperature up to 120 o C and pressures upwards of 3,000
psi, representative of some of the carbonate reservoirs around the world. It
was interesting to note that the capillary number increased by up to 200%
allowing increased recovery of the previously by-passed crude oil. In order to
conduct representative tests of EEOR and SMART EOR, the reservoir tem-
perature, pressure and formation water composition was used in these tests.
The formation water contained approximately 270,000 ppm TDS, allowing
the required current density to be achieved with lower applied voltage.
A comparison of EEOR and SMART EOR results at elevated tempera-
tures and pressures has been summarized below (see figures 4.11 & 4.12 a
and b).
A new index, incremental displacement efficiency to incremental pore
volume injected ratio (Incremental D.E.:PVi index), has been proposed
to track the efficiency of the EEOR and SMART EOR process vs con-
ventional chemical EOR. It was observed that the Incremental D.E.:PVi
index ranged from 2 to 4 for conventional EOR, while ranging from 6
to 10 for EEOR and 15 to 27 for SMART EOR. This provides an indica-
tion of the improved EOR performance as a function of water footprint,
providing a clear justification on the environomics of each tested EOR
process.

4.7 Economics

The laboratory results of power consumption per incremental barrel of oil
produced in reducing OPEX for EEOR on a current density basis are shown

100.0
90.0
80.0
70.0
60.0
50.0
40.0
30.0
20.0
10.0
0.0

Low-acid EOR (WF STAGE)

Low-acid EOR (1.2%+1V/cm STAGE)
EK (WF STAGE)
(WF STAGE)

Low-acid EOR (WF STAGE)
Low-acid EOR (1.2%+1V/cm STAGE)

0 1 2 3 4 5 6 7

Number of injected pore volumes

Figure 4.11 SMART EOR at elevated reservoir temperature and pressure (formation
water composition 270k ppm TDS) - 30% increased oil displacement and more than 50%
reduced water injected