Preparation Of Betaine Gemini Surfactant And Its Performance In Acid Solution

Fracture acidizing is one of the effective technical measures to increase production in the process of carbonate reservoirs development.Control of acid leakoff and homogeneous acidification is the key to success in the process of fracture acidizing.Self-diverting acid diversion acidizing technique is an important method to solve this problem,however,commonly used diversion technology have their own defects,viscoelastic surfactant self-diverting acid diversion acidizing technique because of its simple preparation,gel breaking thoroughly and become a new diversion technology.Currently,tradition Surfactant are widely used for the self-diverting acid,but there are a few reports of zwitterionic Gemini surfactant,let alone for mass production.However,the Gemini surfactant has more excellent properties than traditional surfactant,this paper will research the application of Gemini surfactant in self-diverting acid.A type of zwitterionic gemini surfactant SCB-14 was synthesized with ethylenediamine,1-bromotetradecane,sodium chloroacetate,iodomethane as the main starting materials.The main reactions includes alkylation,carboxyl substitution and quaterisation.In the alkylation process,the optimum reaction conditions were ascertained as follows:n(ethylenediamine):n(1-bromotetradecane)=1:2,the reaction took place at 70℃ for 6h,the yield was 83%.In the carboxyl substitution process,the optimum reaction conditions were ascertained as follows:n(dual secondary amine):n(sodium chloroacetate)= 1:3.8,the reaction took place at 90℃ for 10h,the yield was 80%.In the quaterisation process,the optimum reaction conditions were ascertained as follows:n(dual tertiary amine):n(iodomethane)= 1:8,the reaction took place at 35℃ for 8 h,the yield was 73%.The target product was identified by IR and 1HNMR.The critical micelle concentration is 3.28×10-5mol/L and γcmc is 29.46mN/m at 25°C in aqueous solution.From the relationship between viscosity of SCB-14 and pH,we can see at a shear rate of 170s-1,the viscosity of SCB-14 is 171mPa·s at 60℃ when the dosage of SCB-14 is 5%(mass fraction)and the mass fraction of hydrochloric acid is 2%.Continue to increase the dosage of SCB-14,the viscosity increase a little.Considering the cost,we ascertained the dosage of SCB-14 is 5%.Under certain conditions,the free Ca2+、Mg2+ can increase the viscosity of the system.And Ca2+ has higher capacity to increase the viscosity than Mg2+.At a certain concentration and pH conditions,Fe3 will produce precipitation and drop the viscosity of the system.The viscosity increased first and then decreased when temperature changes.When the temperature is about 50℃,the viscosity reaches a maximum.Environmental scanning electron microscope images indicated that acidizing fluid system under certain conditions can generate larger micelles when micelles intertwined,overlap and extension,and the viscosity of the system increase when film network structure emerged.The experimental apparatus for rotating rock determinated the acid-rock reaction kinetic parameters of SCB-14 acidizing fluid system and hydrochloric acid.The result showed that high-viscosity acid reduced the acid-rock reaction and increased the etching effective distance.