Study On Synthesis,Properties And Applications In Enhanced Oil Recovery (EOR) Of Novel Gemini Surfactant

The tertiary oil recovery research had become important issue,which aimed at improving oil recovery of remainder oil after water flooding.The technology of alkaline/surfactant/polymer (ASP) compound flooding has been developed from the 1980s,which is derived from alkaline flooding,surfactant flooding and polymer flooding.ASP compound flooding not only enhance the displacement efficiency but also can enlarge the sweep volume of displacing phase by the synergistic effect among oil displacement agents.The key technique of ASP compound flooding is how to choose the best surfactants system which can reduce oil/water interfacial tension(IFT) to 10-3mN·m-1 . But surfactants systems which can reduce oil/water IFT to ulrtalow level are not developed in our country now.Oversea corporations have produced a few surfactants systems ,b ut the prices are very expensive and these surfactants systems can not fit to various crude oil and need the help of a great deal alkali.The exploration of surfactants system with high effectiveness,practicability and cheapness has a great significant.Gemini surfactant is a new-style surfactant.Comparaed with conventional surfactants, Gemini surfactants exhibit higher surface activity,lower cmc and high-powered wettability, which make them superior to the sole surfactant employed in EOR area at present. The anionic diaether diphenyl sulfonate(DADPS) Gemini surfactant(Tris(2-hydroxyethyl)ammonium5,5'-(propane-2,2-diyl)bis(2-alkoxybenzenesulfonate)) was synthesized acting as reacting material with bisphnol A,bromo-alkane(containing the number of carbon atom are 10,12,14,16 respectively),chlorosulfonic acid and triethanolamine.The reactions include aetheration reaction,sulfonic reaction and neutralization reaction. Finally, the structures of these Gemini surfactants were identified by Infrared Absorption Spectrometry (IR). Gemini surfactants'surface activities was appraised, the result showed that the cmc of Gemini surfactants are from 0.79 to 1.02 mol·L-1, the surface tension (γcmc)are from 28.4 to 33.2 mN·m-1.The investigation results of Gemini surfactants solution reducing oil/water IFT indicated that this sort of surfactants could reduce water/oil IFT even to ultra low level, which is 10-3 mN·m-1order of magnitude under the condition of without any assistant reagents(except DADPS-10),and the time of maintaining is long. Gemini surfactants had better synergistic effect with alkaline than conventional surfactants, which could maintain ultra low IFT at a wide range of mineralizable degree.The surface property was evaluated by contact angle measuring instrument:The investigation results of anionic Gemini surfactants converting sandstone surface wettability indicated that anionic Gemini surfactants could convert oil-wet (about 110°) into weak water-wet (about 40°). The converting wettability capability of Gemini surfactants is higher than conventional anionic surfactants, but lower than conventional cationic surfactants, and is declining while hydrophobe chain is increasing. The static adsorption experiments were conducted to study the adsorption of surfactants on oil sand at 45℃. The results showed that the adsorption of Gemini surfactants was lower than conventional surfactants, NaOH and the addition of polyacrylamide to further reduce its adsorption on oil sand.Microscopic displacement curse and results of anionic Gemini surfactants'solution indicated that Gemini surfactants solution had high oil displacement efficiency. According to the microscopic displacement curse and results, oil displacement mechanism of anionic Gemini surfactants was put forward, which includes reducing oil/water IFT and converting the wettability of rock surface because the form of molecular deposition filming flooding,and etc.In all, anionic Gemini surfactants were provided with favorable foreground in EOR area.