Development And Performance Evaluation Of High Temperature Acid Corrosion Inhibitor

As an important measure to increase oil and gas production,acid fracturing technology is widely used in oil and gas field industry,but acid also brings serious corrosion problems to string and metal equipment.In the medium and low temperature（T≤120℃）acid environment,adding corrosion inhibitor is a very effective metal anti-corrosion measure.With the continuous progress of oil and gas field exploration technology,the depth of oil and gas wells continues to increase,and the downhole temperature not only reaches or even exceeds 180°C.Conventional acidizing corrosion inhibitors have low corrosion inhibition efficiency and poor dissolution compatibility at high temperature,which can not meet the requirements of high temperature acid corrosion protection.Acidizing corrosion of high temperature deep wells has not been well solved.Therefore,it is urgent to study high temperature and ultra-high temperature acid corrosion inhibitors,which is of great significance to the safe development of high temperature oil and gas fields.In this paper,an acid corrosion inhibitor BQC-G with high temperature resistance was developed,its performance was evaluated,and its corrosion inhibition mechanism was discussed.The main research contents are as follows:The main agent of corrosion inhibitor was synthesized,its structure was characterized,and the synthesis conditions were optimized.Six kinds of quaternary ammonium salt corrosion inhibitors were synthesized in the laboratory by using quaternization reaction,pyridine and quinoline as raw materials,respectively with chloroacetic acid,benzyl chloride and hexadecane bromide.The main agent BQC（benzyl chloride quinoline）with excellent performance was evaluated and optimized by static weight loss experiment.The element and structure of BQC were characterized by elemental analysis,infrared spectroscopy and liquid chromatography.The results showed that the compound was the target product.Through orthogonal experiments,the optimum synthesis conditions of the main inhibitor BQC were obtained,that is,n（quinoline）:n（benzyl chloride）=1:1.20,the reaction temperature was 160°C,and the reaction time was 10 h.The corrosion rate of N80 steel was only 1.43 g/（m²·h）in 20%hydrochloric acid solution with 1.0%BQC at 90°C.On this basis,the effects of corrosion temperature,corrosion time,corrosion inhibitor dosage and acid concentration on the corrosion inhibition performance of BQC were studied.A high temperature acid corrosion inhibitor BQC-G was developed and its performance was evaluated.Through the thermal stability experiment,compatibility experiment and high temperature and high pressure dynamic corrosion experiment,the surfactant and synergist were screened,and their compound dosage was determined.The formula of high temperature acid corrosion inhibitor BQC-G was obtained,that is,87%corrosion inhibitor main agent BQC+5.0%surfactant GTS+3.0%alkynol derivative+5.0%synergist CAP.The corrosion rate of N80 steel was 70.25 g/（m²·h）at 180°C and the addition of corrosion inhibitor BQC-G was 5.0%.The corrosion rate of N80 steel was95.45 g/（m²·h）at 200°C and 5.0%BQC-G.The corrosion inhibitor BQC-G has good compatibility with the acid solution under high temperature conditions,and no layered precipitation occurs.The corrosion inhibition mechanism of high temperature acid corrosion inhibitor BQC-G was investigated.The adsorption morphology and adsorption characteristics of corrosion inhibitors were studied by scanning electron microscopy,atomic force microscopy,EDS and XPS.The results show that the corrosion inhibitor BQC-G can form a complete and dense hydrophobic adsorption film on the surface of N80 steel sheet,which prevents the corrosive medium from contacting the metal surface directly and protects the metal from slowing down the corrosion.The electrochemical behavior of corrosion inhibitor adsorption was studied by electrochemical method.The polarization curve results show that with the increase of corrosion inhibitor BQC-G concentration,the corrosion current density decreases,the self-corrosion potential shifts negatively,and the slope of the cathodic and anodic polarization curves increases.The corrosion inhibitor BQC-G is a mixed corrosion inhibitor mainly inhibiting the cathode.The electrochemical impedance results showed that with the increase of the amount of corrosion inhibitor BQC-G,the mass transfer resistance increased significantly,and the corrosion inhibition rate increased gradually.The results of adsorption isotherm model show that the adsorption behavior of corrosion inhibitor BQC-G on the surface of N80 steel sheet satisfies the Langmuir isotherm,which is dominated by monolayer adsorption and has a geometric coverage effect,ΔG=-35.59 k J·mol^-1.Its adsorption is a spontaneous process,mainly chemical adsorption,accompanied by physical adsorption.