Enhanced Oil Recovery

Polymer flooding is the most widely used Chemical Enhanced Oil Recovery (CEOR) method. It is relatively simple to apply and has a long history of successful field applications. Field implementation requires specialized mixing and injection equipment to avoid polymer degradation and viscosity loss. Most CEOR technologies require the addition of polymer for mobility control.

 

Polymer flooding

Polymer is added to the injection water to increase viscosity which improves sweep efficiency and provides mobility control between water and oil. Polymer flooding can yield a significant increase in oil recovery compared to conventional waterflooding. Polymer is mixed and injected continuously for an extended period of time until about 30 to 50 percents of the reservoir pore volume in the project area have been injected. The polymer slug is followed by continued long-term waterflooding to drive the polymer slug and the oil bank in front of it toward the production wells.

 

 

Chemical Enhanced Recovery

In CEOR, recovery of residual oil is achieved by adding surfactants and alkali to the injection water. Surfactants decrease the interfacial tension between oil and water and alkali agents can be added to generate in-situ surfactants and help to reduce the high level of surfactant adsorption to the reservoir rock. Due to the high pH brought about by the addition of alkali a water softening system is needed to eliminate precipitation of hardness ions.

 

 

Selecting the right polymer

SNF produces a wide range of EOR polymers in both powder and emulsion form. These cover the majority of reservoir conditions. All the polymers used for EOR are anionic and the selection of the best one for a field depends on 3 main parameters; temperature, water composition and permeability. SNF has expertise and guidelines to fine-tune the chemistry in order to limit chemical, mechanical and thermal degradation. SNF EOR polymers include:

  • Anionic co-polymers for below 85°C (185°F)
  • Sulfonated co and ter-polymers for below 100°C (212°F) and/or salty brines
  • N-Vinyl Pyrrolidone based ter-polymers for up to 140°C (284°F)
  • Associative polymers
  • Thermo-associative polymers
  • Iron and H2S resistant polymers
  • Salt resistant polymers
  • Protective packages