Table 1 Summary of laboratory experiments demonstrating the impact of various factors on electrokinetics

[34]

Carbonate: dolomitic limestone

10–25%

0.1mD–16D

Ambient

–

–

36,100 ppm

Cl⁻, H⁺, OH⁻

8–14%

2.0 V/cm

(1) Accumulation of chlorine gas produced at the anode caused a reduction in electroosmotic flow

(2) Porosity, permeability, and clay content identified as key factors affecting electroosmotic flow

[32]

Surrogate sandstone cores

10.2–14.7%

2.16–41.88mD

Ambient

n-Hexane

(SG–0.79)

Kaolinite montmorillonite

58,800 ppm

Na⁺, Cl⁻, Mg²⁺, SO₄²⁻, K⁺, Ca²⁺

3%

1.5 V/cm

(1) Viscous drag of oil was observed on the pore walls due to the electroosmotic effect

(2) Permeability increase due to enlargement of the capillaries

(3) Clay contents between 10 and 15% yielded maximum oil recovery

[2]

Carbonate–mudstones and wackestones

4–27%

0.1–0.2 mD

–

Medium crude

(API–29^°)

–

–

Non-ionic surfactant,

Brine

7%

2.0 V/cm

(1) Simultaneous surfactant flooding yielded a 15% increase in increase in oil recovery compared to sequential flooding

(2) Simultaneous surfactant flooding also consumed more power

[25]

Sandstone

25–26%

200–230 mD

Ambient

Kerosene

6%–Montmorillonite

6%–illite

6%–kaolinite

5000 ppm

Na⁺, Cl⁻

20–113%

5–150 milliamp

(1) Permeability to kerosene increases and remains higher after each electrical stimulation period

(Ansari et al. [20])

Carbonate

8.8–20.33%

0.22 -2.69 mD

80 °C

3000 psi

Medium crude oil (34.5° API, 3.5 cP)

–

Low concentration Acids ( 1.2% HCl)

H⁺, Cl⁻, OH⁻

15–35%

1 V/cm

(1) Combining electrokinetics with low concentration acid flooding resulted in enhanced permeability and displacement efficiency by:

-Improving pore connectivity through electrical conduction

-Enhancing penetration of acid and H⁺ ions deeper into the carbonate reservoirs

[64]

Carbonate

22.3–26.0%

0.57–1.38mD

90 °C

2500psi

Dead oil

(41.5° API)

–

17,545–23,377 ppm

Na⁺, Cl⁻, SO₄²⁻, K⁺, HCO₃⁻

2–4%

10 mA

(1) Applying Eelectrokinetics during secondary recovery proved unsuccessful due to high brine salinity resulting in salt precipitation and formation damage

(2) Gas generation (oxygen and chlorine observed at the anode)

[13]

Carbonate

3–27%

0.1–0.8mD

Ambient

Medium crude

(API–29^°)

–

10,000 ppm

Alkyl polyglycoside (APG)

12–15%

2 V/cm

(1) Oil-wet core plugs consume approximately 10 times more water than water-wet core plugs

(2) Higher EK yield observed in oil-wet reservoirs as EK-assisted sequential surfactant EOR produced 45% of the original recovery factor in oil-wet while producing 14% of original recovery factor in water-wet core-plugs

[5]

Berea Sandstone

20.4–24.3%

30.6–145.4 mD

Ambient

Light–medium oil (26.3–39.3 API)

40,000 ppm

NH₄⁺,Cl⁻

9%

2 V/cm

(1) Reduction in injected water required when DC is applied simultaneously

(2) Improvement in permeability observed

[18]

Carbonate

8–28%

Ambient and 80 °C

3000 psi

Light–medium (34°API-29°API)

–

40,000 ppm

NH₄⁺, Cl⁻, H⁺, OH⁻

13%

0.5–2.0 V/cm

(1) Increase in acid concentration yielded a corresponding increase in displacement efficiency. However, this is limited by the production of CaCl₂ and CO₂ which inhibits oil flow

(2) Higher voltage produces a greater electrokinetic driving force and gives a higher displacement efficiency

(3) The effect of higher voltage is limited by pressure. An increase in pressure causes consolidation and stabilization of currents. This leads to an increase in absorption of ions by the rock surface, decrease in rock resistance and subsequent decrease in electromigration effect

[65]

Sandstone

12.32–12.53%

0.1869–0.32md

Ambient temp and 3375 psi

Synthetic white oil

–

3550–35,500 ppm

Na⁺, Cl⁻

50%

0–15 V

(1) Increase in flow rate observed when voltage was increased until the optimum value of 10 V was reached

(2) Viscous dragging of oil molecules by water was affected by brine salinity

(3) At low brine salinity, oil displacement efficiency is higher for simultaneous flooding whereas, at high brine salinity, the reverse is true