Compatibility, Aqueous Stability, and Phase Behavior of Synthesized Gemini Surfactants with Commercial Surfactants

The main objective of this work was to identify the stability and compatibility of synthesized Gemini surfactants with brine (injection and formation) and commercially available surfactants. Phase behavior has been done in which different types and concentrations of commercial surfactants, and salt solutions of different molarities have been mixed with a constant percentage of crude oil at ambient conditions and at high temperature. This is important to determine the optimum formulation consisting of more than one surfactant for typical reservoir conditions.

In this work, NaCl brine with 9 different salinities has been used for initialization. Then an optimum concentration of NaCl and gemini surfactant has been used with 6 commercial surfactants to check for stability and the one with precipitates has been screened out. Then each of these solutions has been mixed with 30% crude oil and mixed rigorously to observe micro-emulsions. In the last step, different gemini surfactants have been used with each of the 6 commercial surfactants at 9 NaCl concentration to observe the effect of salinity and to determine the optimum salinity.

All the cationic gemini surfactants were compatible with injection brine and formation brine. However, the commercially available internal olefin sulfonate (IOS) surfactant was not compatible with injection and formation brine. Synergism was observed between the synthesized cationic gemini surfactant and IOS surfactants. Commercial IOS surfactants have successfully been dissolved in saline water because of the presence of gemini surfactants. All commercial surfactant has been found stable with the gemini surfactants at high temperature. The gemini surfactant improved the salt tolerance of commercially available surfactant. On the other hand, the olefin sulfonate surfactant improved the microemulsion behavior of cationic gemini surfactant. Most of the emulsions formed at water-in-oil microemulsions.

This work explains how we can improve the salt tolerance and microemulsion behavior of different cationic and anionic surfactants.