Anionic polyacrylamide with high ATBS or AMPS used for EOR (Enhanced Oil Recovery) has become a key chemical solution in modern polymer flooding, especially in harsh reservoir conditions such as high temperature, high salinity, and high divalent ion content. Compared with conventional partially hydrolyzed polyacrylamide (HPAM), anionic polyacrylamide modified with ATBS (2-acrylamido-2-methylpropane sulfonic acid) or AMPS offers superior thermal stability, salt tolerance, and long-term viscosity retention, making it highly suitable for advanced EOR applications.

1. Background: Polymer Flooding in EOR

Polymer flooding is one of the most mature and cost-effective chemical EOR methods. Its primary objective is to increase the viscosity of injected water, thereby improving the mobility ratio between water and oil and enhancing sweep efficiency. Traditional HPAM performs well in low-temperature and low-salinity reservoirs but suffers from viscosity loss, hydrolysis, and degradation under harsh conditions. This limitation has driven the development of anionic polyacrylamide with high ATBS or AMPS content for EOR.

2. Role of ATBS and AMPS in Polymer Structure

ATBS and AMPS are sulfonated monomers incorporated into the polyacrylamide backbone. Their sulfonic acid groups (-SO₃⁻) are strongly anionic and chemically stable.

In anionic polyacrylamide with high ATBS or AMPS used for EOR, these monomers provide several critical advantages:

• Strong resistance to calcium and magnesium ions

• Reduced polymer hydrolysis at elevated temperatures

• Improved molecular rigidity and chain extension

• Enhanced long-term viscosity stability

The sulfonic groups remain ionized even in high-salinity brines, unlike carboxylate groups that can collapse in the presence of divalent cations.

3. Application in High-Salinity Reservoirs

Many mature oilfields targeted for EOR contain formation water with total dissolved solids (TDS) exceeding 50,000–200,000 mg/L. Conventional HPAM loses viscosity rapidly under such conditions.

Anionic polyacrylamide with high ATBS or AMPS used for EOR maintains viscosity due to its sulfonate-based charge structure, which is far less sensitive to ionic strength. This allows effective polymer flooding in offshore reservoirs, Middle East carbonate reservoirs, and saline sandstone formations.

4. Application in High-Temperature Reservoirs

Thermal stability is a critical requirement for EOR polymers in reservoirs with temperatures above 80–120 °C. HPAM undergoes hydrolysis and oxidative degradation, leading to molecular weight reduction and viscosity loss.

The application of anionic polyacrylamide with high ATBS or AMPS used for EOR significantly improves thermal resistance. ATBS and AMPS units reduce chain scission and stabilize the polymer backbone, allowing long-term performance in high-temperature reservoirs, including deep onshore fields and steam-assisted environments.

5. Improved Mobility Control and Sweep Efficiency

The primary function of EOR polymers is mobility control. High-molecular-weight anionic polyacrylamide with ATBS or AMPS provides excellent thickening efficiency at relatively low dosages. The extended polymer chains create higher solution viscosity and elastic behavior, which helps divert injected water into unswept zones.

As a result, anionic polyacrylamide with high ATBS or AMPS used for EOR improves areal and vertical sweep efficiency, mobilizes residual oil, and increases ultimate oil recovery compared with water flooding.

6. Resistance to Mechanical and Shear Degradation

During injection, polymers experience high shear in pumps, tubing, perforations, and near-wellbore regions. Mechanical degradation reduces molecular weight and viscosity.

Polymers containing ATBS or AMPS exhibit enhanced chain rigidity and shear resistance. In the application of anionic polyacrylamide with high ATBS or AMPS used for EOR, this results in better viscosity retention after injection, ensuring that the polymer remains effective deeper in the reservoir.

7. Compatibility with Reservoir Rocks and Fluids

Anionic polyacrylamide with high ATBS or AMPS shows good compatibility with sandstone and carbonate formations. The strong hydration shell around sulfonate groups reduces polymer adsorption on rock surfaces, minimizing chemical loss.

Additionally, these polymers are compatible with oxygen scavengers, biocides, and scale inhibitors commonly used in EOR operations, simplifying field implementation.

8. Field Performance and EOR Results

Field trials and commercial applications have demonstrated that anionic polyacrylamide with high ATBS or AMPS used for EOR can significantly increase incremental oil recovery, often by 5–15% of original oil in place (OOIP). Improved injectivity, stable injection pressure, and sustained oil production have been observed in both sandstone and carbonate reservoirs.

9. Environmental and Operational Advantages

Compared with thermal or gas EOR methods, polymer flooding using ATBS/AMPS-modified polyacrylamide is relatively low-energy and cost-effective. Lower polymer dosages, extended performance life, and reduced frequency of chemical replacement contribute to favorable project economics.

10. Conclusion

Anionic polyacrylamide with high ATBS or AMPS used for EOR represents a significant advancement in polymer flooding technology. Its exceptional resistance to high temperature, high salinity, and divalent ions makes it ideal for challenging reservoirs where conventional HPAM fails. By providing superior mobility control, sweep efficiency, and long-term stability, these advanced polymers play a critical role in extending field life and maximizing oil recovery in modern EOR projects.