Research On AM/APEG/DMC/DMAAC-16 Acid Liquid Retarder And Adsorption Behavior

Acid stimulation technology is an important measure to increase production for low permeability reservoir.The reaction rate of active acid and rock is too fast to do acidizing effectively for far-well zone.Thus,the researchers developed retarded acid such as gelled acid,emulsified acid,foamed acid by adding additive into active acid,which could reduce the reaction rate of acid and rock and improve the effect of the acidizing.However,these retarded acid has many shortcoming such as pumping difficulties,unstable.It is necessary to develop a novel retarded acid to meet the requirement of the need of oil and gas field development.According to the characteristics of the acid-rock reaction,a quadripolymer of acrylamide(AM),[2-(methacryloyloxy)ethyl]-trimethylammonium chloride(DMC),allyl polyethylene glycol(APEG),hexadecyl trimethyl allylammonium chloride(DMAAC-16)were designed and synthesized in this work.Through the single factor experiments we found that the optimum synthesis conditions were:monomer ratio of n n(AM):n(APEG):n(DMC)was 20.00:1.00:4.00,the concentration of hydrophobic monomer was 0.7 mol%,the reaction temperature was 50℃,the quality of monomer initiator(azobisisobtltryamide chloride)was 0.3 wt%,reaction time was 6h,monomer concentration was 25 wt%.The molecular structure of quadripolymer was characterized by Fourier transform infrared(FT-IR)and nuclear magnetic resonance hydrogen spectrum(1H-NMR)spectroscopy.The results indicate that the obtained product is basically consistent to the designed composition,which means that the PAD AD is successfully synthesized.The molecular weight and its distribution of PAD AD was tested by gel permeation chromatography.The results were:Mw was 6.58×104,Mn was 1.22×105 and the molecular weight distribution was 1.85.The intrinsic viscosity of PAD AD was 114.86mL·g-1 by Ubbelohde viscometer.The retarding effect on acid-rock reaction rate of PAD AD was tested through CO2 gas collection device.The duration of the acid-rock reaction was beyond 120 min on both static and dynamic conditions.The duration of the acid-rock reaction could reach 120 min even at 90 ℃.When the concentration of NaCl was 5000 mg·L-1 in the acid system,the duration of the acid-rock reaction was still 120 min.When the acid system has 5000 mg·L-1 CaCl2,the property of PAD AD would be improved.When the concentration of PAD AD was 0.7 wt%in the 20%HCl,the viscosity of the acid syetem was lower than 15 mPa·s.We researched the microstrcuture of carbonate rocks before and after corrosion by different acid systems,we found the PAD AD could adsorbed effectively on the surface of the carbonate rock and reduce the acid-rock reaction rate.The adsorption behavior of PAD AD on the surface of carbonate rock was researched.The kinetic model of PADAD on the surface of carbonate rock was fitting the pseudo-second-order kinetic model and the adsorption process was physical adsorption.The thermodynamic model of PADAD on the surface of carbonate rock was fitting Freundlich model and the adsorption process was multilayer adsorption.