EOR/IOR terminology – time for a (real) change?
EOR vs. IOR – Time for a Change. On August 1, 2024, the SPE community issued a call for public input on proposed changes to IOR/EOR terminology. Surveys revealed a limited understanding of these terms, highlighting the need for clearer definitions. However, the new proposals—introducing an additional term, AOR (Assisted Oil Recovery)—have raised concerns about adding complexity rather than simplifying the existing framework.
The real question is: Why not completely overhaul the terminology to make it more intuitive and reflective of modern recovery techniques?
Why Words Matter in Oil Recovery
The language we use shapes industry practices, influences decision-making, and drives oilfield development strategies. The long-standing Primary, Secondary, and Tertiary Recovery model has been the foundation of reservoir and petroleum engineering for decades. However, its staged approach limits innovation, encouraging companies to repeat outdated strategies rather than embracing a full-field, lifecycle-optimized approach.
The Problem with the Traditional Recovery Model
1️⃣ Low Recovery Factors Persist
- The IEA reports an average recovery factor of 30%, leaving 70% of oil untapped—despite nearly a century of advancements in oil recovery.
- Waterflooding alone is insufficient, yet it remains the default method before considering EOR.
2️⃣ Excessive Water Production
- Secondary recovery often produces 5 to 14 barrels of water per barrel of oil, increasing energy consumption and CO2 emissions.
- Engineers must question why waterflooding is prioritized without immediate support from complementary recovery methods.
3️⃣ Delayed & Less Effective EOR Applications
- Heterogeneous reservoirs guarantee conformance issues, yet they are often ignored until water breakthrough occurs.
- Once a reservoir reaches its brownfield stage, additional recovery techniques become less effective and less economically viable.
Surface-Controlled Recovery (SCR) / Reservoir Access Enhancements (RAE)
Interventions that optimize recovery at the surface or wellbore level, without modifying reservoir characteristics. Includes:
✅ Pattern & fluid sweep adjustments
✅ Drilling & well interventions
✅ Production mechanics improvements
These methods can be applied at any stage of a reservoir’s life.
Subsurface Injection Recovery (SIR) / Injection-Based Enhancements (IBE)
Techniques that involve injecting fluids into the reservoir to enhance recovery. Divided into:
🔹 Native Fluid Injection (NFI)
Injection of fluids naturally present in the reservoir, used primarily for pressure maintenance and displacement efficiency. Includes:
✅ Water Injection (produced water, aquifer water)
✅ Gas Injection (produced gas, associated gas)
🔹 Non-Native Fluid Injection (NNFI)
Injection of fluids not originally present in the reservoir, used to alter reservoir properties or improve displacement efficiency. Includes:
✅ Chemical Injection – Polymer, surfactant-polymer (SP), alkaline-surfactant-polymer (ASP), microbial EOR (MEOR)
✅ Gas Injection (Non-Native) – CO₂, nitrogen, hydrocarbon gases (propane, butane), Water-Alternating-Gas (WAG)
✅ Thermal Methods – Steam injection, in-situ combustion, cyclic steam, SAGD
✅ Other Energy-Based Techniques – Microwave energy, acoustic wave energy
EOR vs. IOR – Why This Change is Needed
By removing outdated “Primary, Secondary, and Tertiary” labels, this new classification:
✔ Reflects modern EOR applications instead of forcing them into rigid stages.
✔ Encourages full-lifecycle recovery optimization, rather than maximizing NPV at each stage.
✔ Simplifies recovery terminology while maintaining technical accuracy.
✔ Aligns industry practices with real-world reservoir behavior and technological advancements.
Final Thoughts – A Call for Industry-Wide Change
Reforming IOR/EOR terminology is not just about semantics—it’s about changing the way we approach oil recovery. By adopting a more intuitive, scientifically accurate framework, the industry can increase recovery rates, minimize water production, and integrate conformance solutions from the start.
Change won’t be easy—terminology shapes mindsets, and mindsets influence strategy. However, with momentum already building, this is the right time to redefine oil recovery for a more efficient, sustainable future.
Keywords:
Enhanced Oil Recovery (EOR), Improved Oil Recovery (IOR), Assisted Oil Recovery (AOR), Reservoir Engineering, Oil Recovery Techniques, Waterflooding, Oil Production Optimization, Oilfield Development
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