posted on 2024-02-27, 19:06authored byJian Hou, Tianping Huang, Mohammed Alotaibi, Abdulkareem AlSofi
Surfactants with
stable chemical structures and robust ability
are required to lower interfacial tension and stabilize emulsions
for successful chemical injection applications. This work selected
six surfactants, dodecyl carboxylic sodium (LAS), dodecyl sulfonate
dodecyl sodium (SLS), dodecyl sulfate sodium (SDS), dodecyltrimethylammonium
bromide (DTAB), 3-(N,N-dimethylmyristylammonio)
propanesulfonate (SB3–14) and a sulfobetaine formulation (PCT-10),
and systematically investigated the ionic-type effects on thermal
stability at 95 °C for 150 days in high-salinity water (total
dissolved solids (TDS) = 57,600 ppm). With characterizations of aged
samples performed through a spinning drop tensiometer, high-performance
liquid chromatography, and infrared spectroscopy, it can be seen that
the long-term stability sequence of ionic surfactants in solutions
is sulfobetaine ≈ quaternary ammonium > sulfonate > sulfate
>
carboxylate. The carboxylate possibly precipitates out from the solution
in the acid form, and the sulfonate and sulfate decompositions are
due to the hydrolysis of the anionic head, forming alcohol and NaHSO3/NaHSO4. Obvious decomposition of sulfobetaine
and quaternary ammonium was not observed, but these molecules might
suffer the elimination of the ionic head, forming the corresponding
alkene and amine. The results also show that the dissolved oxygen
in the solution preparation significantly sped up the degradation
of sulfonates. At last, the emulsion stability tests of crude oil
in surfactant solutions showed that sulfobetaine surfactants retained
the highest emulsifying ability after thermal aging and thus are promising
candidates for long-term chemical injection in high-temperature high-salinity
reservoirs.