Performance Evaluation And Microscopic Mechanism Research For Acidification Inhibitor

Acidizing fluid is often used to enhance oil recovery in oil field development,the resulting corrosion of metal equipment has got widespread attention.Acidification inhibitor as high efficiency,low cost,easy to use chemical additives in the oilfield has been widely used in the oil production process.However,the inhibition effect of acidification inhibitor is influenced by many conditions,such as temperature,pressure,concentration,corrosive medium.Corrosion inhibitors in different conditions have different performance.In this paper,a series of researches are carried out on the problems of the acid corrosion inhibitor in Shengli Oilfield,such as fuzzy concentration,unclear mechanism of corrosion inhibition and low efficiency of corrosion inhibition.Five kinds of acid corrosion inhibitors were evaluated under different conditions by weight loss method.It was found that the inhibition efficiency?IE?of the five kinds of acid corrosion inhibitors on N80 steel were 90%above at 90?,atmospheric pressure and 15%concentration hydrogen chloride.IE is as follows:A=B>D>C>E.The inhibition effect of the inhibitors on N80 steel is generally at 120?,16MPa,15%concentration hydrogen chloride and other additives.The corrosion rate of the steel sheet was still too large to meet the requirements in the experiment with the addition of corrosion inhibitor.IE is as follows:A>D>B>C>E.Additionally,the temperature has a great influence on the performance of the corrosion inhibitor.The molecular structure of the corrosion inhibitor is easy to decompose under high temperature.So,the operating temperature of the inhibitor A should not exceed 140?.Corrosion coupons were observed using a metallographic microscope.It was found that the inhibitors A,B both inhibit the uniform corrosion of N80 steel and pitting corrosion.The extent of pitting damage to metal is the smallest in the presence of the inhibitor B.Electrochemical methods were used to study the electrochemical mechanism of corrosion inhibitors.It was found that the inhibitors A,B,C and D were mixed corrosion inhibitors and the inhibitor E was anodic corrosion inhibitors.Corrosion inhibitors play a role in corrosion inhibition by adsorption on the metal surface.On one hand,corrosion inhibitors hinder the charge transfer.On the other hand,it inhibits the proliferation of ions?iron ions and corrosive media particles?.Corrosion inhibitor A molecules may be through the role of hydrogen ions to prevent hydrogen ions to be electron is reduced to achieve the purpose of inhibiting corrosion.The other four corrosion inhibitors may inhibit corrosion by inhibiting the diffusion of ions?ferric ions and corrosive medium particles?,and also form a passivation film on the metal surface to achieve corrosion inhibition.The corrosion inhibitors were studied by molecular simulation.The results of quantum chemical calculations show that the interaction between corrosion inhibitor and metal surface is mainly due to corrosion inhibitor molecules get electrons and metal surface atoms lose electrons.According to E_LUMO,chemical potential and electrophilic index,it is concluded that the performance of corrosion inhibitors from good to bad follows:A>B>D>C>E.Molecular dynamics simulation results show that the order of single molecule adsorption energy of the five inhibitors on the metal surface was A>B>C>D>E.The diffusion coefficient of corrosion inhibitors for the inhibition of hydrogen ion diffusion is A<B<D<C<E.This is consistent with the conclusion obtained through experimental methods.