Development Of Dual Mannich Base Corrosion Inhibitor And Its Performance Evaluation

Acidification is an important measure to improve hydrocarbon recovery in the exploiting process of oil and gas wells. However, due to the acid injection, it will cause corrosion on the surface of down-hole and tubing equipment,which caused hydrogen embroilment cracking or brittle fracture, causing serious economic losses.Thus acid inhibitors, which has the abilities of good inhibition effect, low cost and environmental resistance, have been utilized during the acidification. Nowadays, Mannich base has been important research topics of acid inhibitors because of its small molecular and containing lone pair of electrons of nitrogen and oxygen atoms, In order to against the problems of exist coke, layered, insufficient dissolved and less stable modification of Mannich bases of high temperature acidification inhibitor, one kind of new Double Mannich base was synthesized, and which behaves efficient, good dissolved dispersion and adapted variety of corrosive environment abilities.Mannich base intermediate was synthesized with ormaldehyde, acetophenone, benzylamine, then added benzyl chloride, ketones and aldehydes to continue to synthesis Mannich base quaternary ammonium salt and Double Mannich base inhibitor.The single factor and orthogonal experiments indicated that the optimum synthesis conditions were as follows:n (Intermediate):n (formaldehyde):n (ketone)=1:1.2:1.2, the reaction temperature was 110?, reaction time was 8h, the pH of medium was 3. Double Mannich base was characterized by IR and 1H NMR. With the inhibitor concentration of 0.5% and the temperature of 90?, the corrosion rate of P110 reached 0.932g/m2·h in 20% hydrochloric acid solution. According to the SY/T 5405-1996 standard, the dissolution and dispersion properties and storage performance of Double Mannich base were also measured, which showed that it had excellent corrosion properties and fine dissolved dispersion.The influence of medium temperature, corrosion time, the concentrations of inhibitor and media conditions (soil acid, thickening acid) was tested by static weight loss. The comparison between Double Mannich base and Mannich base quaternary ammonium salt showed that Double Mannich base had better corrosion performance, and it had the advantages of stability in high temperature and acid, high efficiency and long-time protection. The properties of fog resist was evaluated by neutral drip reaction at different temperature, media concentrations and different concentrations of inhibitor. The results showed that the inhibitor had good fog resist efficiency:under the temperature of 90?, fog resist efficiency reached 93.02%, and when the concentration of HCl was 25%, the fog resist efficiency reached 89.30%.The inhibition mechanism of Double Mannich base were discussed by Electrochemical methods, SEM, electron spectroscopy, dynamic behavior and thermodynamic behavior. The results showed that the Double Mannich base was one kind of mixture of inhibiting corrosion inhibitor and it had good electrode reaction inhibition at cathode under low concentration (0.2%), the electrode and dielectric resistance mainly came from the metal/thin layer interface pole technology. There was phenomenon of extreme value of the concentration. Adding the ions of SO42-?Fe3+?Cu2+ had damaging effects on corrosion performance of Double Mannich base, while PO43- promoted the corrosion inhibitor performance. The adsorption behavior of Double Mannich base obey Langmuir adsorption isotherm and its mainly adsorption type was chemical adsorption and the dissolution of the steel in the acid is an endothermic process.