Oilfield development has three main stages. Primary recovery uses natural formation pressure to let oil flow freely, while secondary recovery injects water to maintain underground energy. However, these two methods only recover about 30% of the underground crude oil, leaving most of it trapped in rock pores. Polymer flooding, a key technology for tertiary oil recovery, injects polymer solution to increase water viscosity and improve oil displacement, effectively flushing out the hard‑to‑extract remaining oil and greatly boosting the overall oil recovery rate.
(1). Working Principle: Making Oil Displacement More Uniform and Efficient
The core of polymer flooding is viscosity enhancement, profile modification, and efficiency improvement. Adding a small amount of polyacrylamide to the injected water significantly increases the viscosity of the aqueous solution, reduces water permeability, and solves the problems of “channeling” and “finding” in ordinary water injection, allowing the displacement fluid to sweep more evenly across the oil layer, leaving no residual oil in corners. Simultaneously, the viscoelastic properties of the polymer strip away the oil film on the rock surface and promote the flow of oil droplets in pores, balancing the expansion of the swept volume with improved oil washing efficiency, further increasing the recovery rate by 10-20 percentage points on top of water flooding.
(2). Core Material: Polyacrylamide (HPAM)
The most commonly used and mature oil displacement polymer in industry is partially hydrolyzed polyacrylamide (HPAM). It has good water solubility, significant viscosity-enhancing effect, and controllable cost, making it suitable for most conventional oil reservoir conditions. Domestic researchers have developed modified products—including temperature‑resistant, salt‑resistant, hydrophobic‑associative, and fast‑dissolving polymers—for complex reservoirs characterized by high temperature, high salinity, and low permeability. These products offer stable performance, stronger adaptability, and meet the stringent requirements of different formations.
(3). Technical Process: Simple and Clear
- Solution Preparation: The polymer dry powder is fully dissolved in water to prepare a homogeneous solution;
- Injection: Pumped into the underground oil layer through a water injection well;
- Oil Displacement: The polymer fluid propels forward, displacing crude oil and flowing towards the production well;
- Production: Crude oil and part of the displacement fluid are produced together and separated and processed at the surface.
(4). Application Value: The “Ballast” for Stable Production in Old Oilfields
Polymer flooding technology is mature and boasts a high input-output ratio. Polymer enhanced oil recovery (PEOR) technology is mature and has a high input-output ratio. It is a key technology for stabilizing oil production, controlling water cut, and extending the lifespan of old oilfields in my country after they enter the high water-cut stage. Currently, it is widely used in large industrial oilfields, including Daqing, Shengli, and Xinjiang, increasing oil production by tens of millions of tons annually. This revitalizes “depleted oilfields” into “high-efficiency production areas,” playing a crucial role in ensuring national energy security and improving resource utilization efficiency.
(5). Future Development
More Efficient and Greener. The industry is upgrading toward composite flooding, intelligent flooding, and green flooding:
- it compounds polymers and surfactants to form binary/ternary composite flooding and further improves development efficiency;
- it applies intelligent injection and online monitoring to achieve precise control;
- it continuously develops new biodegradable, low‑damage, and extreme‑environment‑resistant polymers and steadily expands their application scenarios.