An overview of the concept of Enhanced Oil Recovery (EOR), including its importance in maximizing oil production, the various EOR techniques, and the challenges associated with implementing EOR in oil fields.
Introduction to Enhanced Oil Recovery (EOR)
Graduate‑level overview – concise, organized, and ready for study.
| Aspect | Conventional Production | Limitation |
|---|---|---|
| Primary recovery | Natural reservoir pressure drives oil to the wellbore. | Typically recovers 5–15 % of original oil in place (OOIP). |
| Secondary recovery | Water or gas injection maintains pressure. | Boosts recovery to 30–40 % of OOIP. |
| Enhanced Oil Recovery (EOR) | Any technique that alters fluid/rock properties to mobilize additional oil after primary & secondary stages. | Targets the remaining 60–70 % of OOIP that is trapped by capillary forces, viscosity, or heterogeneity. |
| Method | Primary Physical Principle | Typical Reservoir Conditions | Key Advantages | Typical Limitations |
|---|---|---|---|---|
| Thermal (Steam) EOR | Viscosity reduction by heating heavy oil; steam expands and pushes oil. | Heavy, high‑viscosity oil (API < 20), shallow to moderate depth. | Large incremental recovery (10‑30 % of OOIP); well‑established. | High energy cost; water‑resource intensive; not suitable for light oil. |
| Gas‑Based EOR | 1) Gas injection – miscibility reduces IFT; 2) CO₂ flooding – miscible or immiscible displacement. | Light to medium oil; moderate to high reservoir pressure; good reservoir permeability. | Can achieve high recovery (up to 50 % OOIP); CO₂ provides sequestration benefit. | Requires large gas volumes; miscibility pressure may be high; CO₂ handling and corrosion issues. |
| Chemical EOR | 1) Polymer flooding – increase water viscosity → mobility control. 2) Surfactant flooding – lower IFT. 3) Alkali‑surfactant‑polymer (ASP) – combined effects. |
Light to medium oil; moderate temperature (< 100 °C); adequate permeability (> 10 mD). | Flexible formulation; can be tailored to specific rock/fluid properties. | High chemical cost; adsorption loss; potential formation damage; requires careful design. |
| Micro‑/Nanofluid EOR | Nanoparticles modify wettability, reduce IFT, and improve conformance. | Emerging; applicable to a range of oil types. | Small volumes, high surface activity; can be combined with other EOR. | Limited field data; cost of nanomaterials; stability concerns. |
| Hybrid / Sequential Methods | Combination of two or more techniques (e.g., thermal + chemical). | Tailored to complex reservoirs. | Synergistic effects; can overcome individual method limits. | Higher operational complexity; integrated design needed. |