Anionic polyacrylamide of FLOPAAM 3630S can be replaced by Chinfafloc A3020 

FLOPAAM is a kind of anionic polyacrylamide with 25-30 hydrolysis degree and 20 million molecular weight,mainly used for enhanced oil recovery .

Anionic polyacrylamide (APAM) is a water-soluble polymer that plays a significant role in Enhanced Oil Recovery (EOR) processes. EOR is a method used to increase the amount of crude oil that can be extracted from an oil field, often after the primary and secondary recovery techniques have been exhausted. The application of anionic polyacrylamide in EOR is specifically related to its ability to improve the efficiency of water flooding and assist in mobilizing trapped oil within the reservoir.

1. Introduction to Anionic Polyacrylamide (APAM)

Anionic polyacrylamide is a polymer composed of acrylamide monomers with a negative charge due to the incorporation of anionic groups, such as carboxyl or sulfate groups, in the polymer chain. Its structure provides high water solubility and a significant ability to interact with charged surfaces and particles within the reservoir. The high molecular weight of APAM enhances its viscosity when dissolved in water, which makes it particularly useful in EOR techniques like water flooding and chemical flooding.

Water flooding, one of the most commonly employed secondary recovery methods, involves injecting water into the reservoir to maintain pressure and help push the oil toward production wells. However, water flooding is often inefficient because the injected water tends to bypass the oil or channel through fractures, leaving a substantial amount of oil behind. Anionic polyacrylamide is used in this context to improve water displacement and reduce the tendency of the water to bypass oil, thereby increasing recovery rates.

2. Role of Anionic Polyacrylamide in EOR

The main application of anionic polyacrylamide in EOR is to enhance the mobility control of water injected into the reservoir. The polymer’s ability to increase the viscosity of the injected water is a key factor in its effectiveness. When APAM is added to the injection water, it increases the resistance to flow, causing the water to flow more uniformly through the porous media. This is essential for improving the sweep efficiency of the injected water, ensuring that more oil is displaced towards the production wells.

2.1 Viscosity Modification

The high molecular weight and anionic nature of polyacrylamide significantly increase the viscosity of water when dissolved. The increased viscosity reduces the mobility of water in the reservoir, which is crucial for improving the displacement efficiency during water flooding. By increasing the resistance to flow, the polymer ensures that the injected water flows more evenly through the reservoir rather than following high-permeability pathways that could bypass oil pockets. This means more oil is swept out from the reservoir.

2.2 Wettability Alteration

Anionic polyacrylamide also has the potential to alter the wettability of reservoir rocks. In many oil reservoirs, the rock surfaces are naturally water-wet, meaning water tends to adhere to the rock more readily than oil. This makes it harder for the injected water to displace the oil. However, when polyacrylamide is used, it can modify the wettability of the rock, making it more oil-wet. This enhances the capillary forces that allow oil to move more easily toward the production wells.

2.3 Interfacial Tension Reduction

Another way anionic polyacrylamide contributes to EOR is by reducing the interfacial tension between water and oil. By lowering the interfacial tension, the polymer helps oil droplets to detach more easily from the reservoir rock and become more mobile. This is especially beneficial in fractured reservoirs or in reservoirs where oil is tightly bound to the rock surfaces.

3. Specific EOR Techniques Using Anionic Polyacrylamide

Several EOR techniques utilize the properties of anionic polyacrylamide to improve recovery rates. The most notable technique is water flooding, but polyacrylamide is also used in other chemical EOR methods such as surfactant-polymer flooding and polymer flooding.

3.1 Polymer Flooding

Polymer flooding is a common EOR method in which water is injected into the reservoir with added polymer, such as anionic polyacrylamide, to increase the viscosity of the injection fluid. The polymer helps to improve the sweep efficiency of the water by reducing the tendency of the injected fluid to bypass oil-rich regions. APAM’s ability to increase the viscosity of the water while maintaining its ability to flow through the reservoir makes it particularly effective in this type of flooding.

Polymer flooding is particularly effective in reservoirs with high permeability contrasts, where some areas of the reservoir may be much more permeable than others. Without the added polymer, water would flow too easily through the high-permeability areas and bypass the oil in less permeable zones. By increasing the water’s viscosity, the polymer helps to balance the flow and push oil from the less permeable zones toward the production wells.

3.2 Surfactant-Polymer Flooding

In surfactant-polymer flooding, anionic polyacrylamide is used in combination with surfactants, which reduce the interfacial tension between the water and oil. The surfactants allow the water to more easily detach the oil from the rock surfaces, while the polyacrylamide maintains the viscosity of the injected water. The combination of the two components improves both the displacement efficiency (due to the viscosity modification) and the mobility of oil (due to the reduction in interfacial tension).

3.3 Hybrid Flooding

A newer approach in EOR involves the use of hybrid systems that combine polymer flooding with other techniques, such as CO2 injection or alkaline flooding. In these hybrid methods, anionic polyacrylamide plays a similar role in improving water’s viscosity and mobility, ensuring that the injected fluids move uniformly through the reservoir. Hybrid systems are often used in reservoirs with complex geology or when other EOR methods, like CO2 injection, are not as effective on their own.

4. Benefits of Anionic Polyacrylamide in EOR

The primary benefits of using anionic polyacrylamide in EOR processes are:

1. Enhanced Recovery Efficiency: The polymer’s ability to increase the viscosity of water and modify its flow characteristics improves the overall sweep efficiency of water flooding. This results in a higher percentage of oil being displaced from the reservoir and produced.

2. Cost-Effectiveness: Anionic polyacrylamide is relatively inexpensive and easy to produce in large quantities. Its use can significantly increase recovery rates without the need for costly equipment or more invasive techniques.

3. Compatibility with Reservoir Conditions: APAM can be tailored to work effectively under various reservoir conditions, including different salinity levels and temperatures. This versatility makes it suitable for a wide range of oil fields.

4. Environmental Considerations: Anionic polyacrylamide is generally considered environmentally safe, especially when compared to other chemical additives used in EOR. It breaks down into non-toxic by-products over time, reducing the risk of long-term environmental contamination.

5. Challenges and Limitations

While anionic polyacrylamide has proven effective in many EOR applications, there are several challenges and limitations associated with its use:

1. Shear Degradation: The high molecular weight of APAM polymers makes them susceptible to shear degradation when subjected to high fluid velocities, which can reduce their effectiveness. To overcome this, polymer concentrations must be carefully managed, and pumping rates need to be optimized.

2. Salinity and Hardness Sensitivity: In high-salinity or hard-water reservoirs, polyacrylamide may lose its effectiveness due to the screening effect of divalent ions such as calcium and magnesium. To address this, adjustments in polymer formulations or the use of stabilizers may be necessary.

3. Cost of Injection: Although polyacrylamide is relatively inexpensive, the overall cost of implementing polymer flooding can be significant due to the need for additional infrastructure, equipment, and ongoing injection operations.

6. Conclusion

Anionic polyacrylamide plays a crucial role in enhancing oil recovery through water flooding and other chemical EOR techniques. Its primary function is to increase the viscosity of the injected water, thereby improving the sweep efficiency and ensuring more oil is displaced towards production wells. In combination with other techniques like surfactant-polymer flooding, APAM can further enhance oil recovery by reducing interfacial tension and altering wettability.

Despite its benefits, the application of anionic polyacrylamide in EOR faces some challenges, particularly in high-salinity reservoirs or when dealing with shear degradation. However, with ongoing research and the development of more advanced formulations, the role of polyacrylamide in EOR will likely continue to grow, contributing to more efficient and sustainable oil recovery methods.