Stop or Continue? How Much Pore Volume to Inject in Polymer Flooding

📌 How Much Pore Volume in Polymer Flooding? How do you decide when to stop polymer flooding? In a previous post, I highlighted why resuming water injection after polymer injection is a bad idea—it simply worsens the project’s economics and recovery efficiency. But this raises an even bigger question: How much polymer should you inject before stopping?

The Theory vs. The Reality

📖 According to theory, the larger the Pore Volume (PV) injected, the better:
✔ Retention losses need to be accounted for
✔ Efficient oil displacement requires sufficient polymer injection

So, in theory, 1PV + retention should be the optimal amount. But let’s be honest—economists don’t like that answer(😒).

A Smarter Approach: Annual Project Evaluation

Rather than locking into a 10-year plan, a more flexible, data-driven approach is recommended:

✅ Is the polymer flood technically working?
✅ Is the project economically viable under current conditions? (i.e., is the oil production covering CAPEX & OPEX?)

How to Determine the Optimal Stop Point?

A useful reference is SPE190175, which analyzed polymer flooding in the Captain field using a cumulative polymer injected vs. cumulative (incremental) oil curve.

📊 Key Takeaway:
✔ The curve follows a parabolic shape—initially, more polymer injection leads to higher oil production.
✔ At an inflexion point, efficiency starts declining.
✔ Injection should stop when the curve crosses the economic limit (e.g., 5 lbs polymer/bbl oil = 2.27 kg/bbl).

Beyond a Single Success Criterion

I believe this curve is an excellent tool, but it should not be the only success criterion. Why?

📌 Success depends on multiple factors, including:
🔹 When polymer injection started (Primary vs. Secondary production)
🔹 Oil price fluctuations—Even low incremental production can be profitable at high oil prices

Refining the Decision-Making Process

To improve evaluation, I would recommend tracking three additional key parameters alongside the cumulative polymer injected vs. oil production curve:

📌 Recovery Factor (RF) at time “t”. How much of the reservoir’s oil has been recovered?
📌 Injected Pore Volume (PV) at time “t”. How much polymer has actually been injected compared to the reservoir’s pore volume?
📌 Profitability Index (PI) – $ Revenue from oil sales / $ Spent on polymer injection

When to Stop (or Continue) Polymer Injection?

💡 At the inflexion point, two key questions should be asked:

1️⃣ Was polymer injected efficiently?

• If only 20% of PV has been injected and polymer is already appearing in production wells, something wasn’t designed optimally (e.g., low viscosity, fractures, high permeability streaks).
• In this case, it may be possible to adjust the flood design and continue.

2️⃣ Is the drop in profitability due to external factors?

• If the oil price drops but the flood is technically working, the best strategy (when possible) is to reduce injection and production rates rather than stopping polymer injection completely.

Final Thoughts – The “Stop or Continue?” Framework for Polymer Flooding

✅ Annual health check-ups ensure both technical and economic viability.
✅ Using inflexion points instead of rigid limits allows for more data-driven decision-making.
✅ Adjustments should be made based on observed retention, viscosity propagation, and production response.

For more content, discussions, visit the Polymer flooding Website.

I also extensively discuss these aspects in my training course available on the Polymer Flooding Academy website.

Keywords:

Polymer Flooding, Chemical EOR, Pore Volume Injection, Polymer Retention, Oil Recovery Optimization, Enhanced Oil Recovery, Reservoir Engineering, CAPEX vs. OPEX in EOR, Profitability Index in Oil Production