Surfactant Injection to Increase Recovery Factor

Basic Concept of Surfactant Injection
Surfactant is chemical material which has ability to dissolve oil in water by forming emulsion. Without surfactant, oil is always separated from water and it’s impossible to dissolve. The irreducible oil in the reservoir is trapped and can’t be pushed by water as oil and water has high interfacial tension. Surfactant can change Inter Facial Tension between oil and water allowing the irreducible oil to move together with water. There are three methods of using surfactant to recover the irreducible oil which are stimulation, Huff and Puff and Flooding.

Stimulation is a process to clean up pores surrounding wellbores. The surfactant is dissolved in oil to form surfactant solution. The solution is injected into wellbores and penetrates perforated zones to clean up cakes and scales attached to the perforation holes. The surfactant solution is soaked for few days to allow it reacts with cakes and scales. Surfactant used in the stimulation is generally oil dissolved surfactant. Cakes and scales formed by irreducible oil and debris are cleaned by the surfactant solution. Clean perforation holes allow more oil to flow into a wellbore.

Huff and Puff is similar with Stimulation except Huff and Puff has deeper invasion. In the Huff and Puff method, surfactant solution could reach 10 meters away from well bore. The surfactant solution is soaked for 3 or 4 days and then the well is reopened to produce. The surfactant will flow back to the well carrying irreducible oil. In this method, production of neighboring wells could also increase because of some surfactant leaks to the well.

EOR method consists of producing and injection wells. Surfactant solution is injected into injection well and flows into the reservoir system. The surfactant solution with oil and water is recovered from producing wells. Each injection well has many producing wells to capture the response of the injection. Location of producing and injection wells is normally a radial pattern. The response of EOR injection takes much longer than well stimulation or Huff and Puff. However, EOR process is continuous so once the system is set up, we don’t need work over anymore.

General problems of surfactant injection are salinity and temperature. Surfactant will precipitate when it meets saline formation water. Higher salinity formation water will create more solids resulted from precipitation reaction. The particles produced could block pore spaces and plug the entire reservoir system and endanger the production. This danger makes surfactant injection was not popular until an improved performance surfactant which has salinity resistance performance is discovered. The other problem of surfactant is low operating temperature. The old surfactant has maximum operating temperature of only about 70 oC. The improved performance surfactant should has maximum operating temperature more than 200 oC. The surfactant for well injection has therefore salinity resistance and high operating temperature performances.