Sodium Methallyl Sulfonate (SMAS) is used as an oil displacement agent primarily by improving the rheological properties of aqueous solutions and reducing the interfacial tension between oil and water to enhance crude oil recovery. Below are the specific usage methods and key considerations:
1. Mechanism of Action
- Viscosity Enhancement: When combined with polymers (e.g., partially hydrolyzed polyacrylamide, HPAM), it increases solution viscosity, improving sweep efficiency.
- Interfacial Activity: Reduces oil-water interfacial tension, aiding in the detachment of crude oil from rock surfaces.
- Temperature and Salt Resistance: Suitable for high-temperature, high-salinity reservoirs.
2. Application Methods
(1) Polymer Flooding Formulation
- Example Formulation:
- Main agent: HPAM (1000-2000 mg/L)
- Additive: SMAS (50-200 mg/L)
- Solvent: Injection water (salinity should match reservoir conditions).
- Procedure:
- Dissolve SMAS and polymer together in water under stirring until homogeneous.
- Inject the solution into the reservoir via injection pumps, typically in a slug (0.1-0.3 pore volume).
(2) Surfactant Flooding
- Blend with sulfonate surfactants (e.g., petroleum sulfonate) at a ratio of 1:1 to 1:3, with a total concentration of 0.1%-0.5%.
3. Optimal Conditions
- Reservoir Temperature: ≤120°C (stability should be tested at higher temperatures).
- Salinity: Good salt tolerance, but avoid excessive divalent ions (Ca²⁺, Mg²⁺); chelating agents (e.g., EDTA) can be added if needed.
- pH Range: 7-10 (alkaline conditions enhance performance).
4. Key Considerations
- Compatibility Testing: Conduct core flooding experiments to evaluate compatibility and displacement efficiency.
- Adsorption Loss: SMAS may adsorb onto rock surfaces; pre-flushing (e.g., with low-salinity water) can minimize losses.
- Environmental Compliance: Monitor residual concentrations to meet discharge standards.
5. Field Application Cases
- Daqing Oilfield (China): SMAS + HPAM increased recovery by 8%-15%.
- Middle East High-Salinity Fields: Used as a salt-resistant additive, improving displacement efficiency by over 10%.
6. Optimization Recommendations
- Nanocomposite Formulations: Combine with SiO₂ nanoparticles to enhance stability.
- Alternate Injection: Use with gas flooding (e.g., CO₂) for improved microscopic displacement efficiency.
By optimizing formulations and operational parameters, SMAS can effectively enhance oil recovery in tertiary recovery (EOR) processes. However, laboratory simulations should precede field-scale applications to ensure suitability for specific reservoir conditions.
