Research On Preparation And Mechanism Of Inhibitor For Hydrochloric Acid And High Temperature Carbon Dioxide

Corrosion is an inevitable problem in oil field industry.The acidic environment brought about by reservoir conditions and production processes can cause corrosion of equipment and pipelines,leading to large number of economic losses and production risks.Corrosion inhibitors,as a low-cost and easy-to-operate corrosion inhibition technology,have great significance for metal protection in oilfield exploitation.With the increase in the depth of reservoir development in recent years,the demand for corrosion inhibitors for high-temperature environments has become more and more urgent.High temperature corrosion inhibitor research is needed.This thesis aims at the problems of hydrochloric acid corrosion and carbon dioxide corrosion at high temperature,design and synthesis of corrosion inhibitor molecules that yields formulation for high temperature corrosion inhibitor.On this basis,through the combination of theoretical calculations and actual experiments,the mechanism of corrosion inhibitors is deeply understood.This work provides an effective solution for the protection of high temperature hydrochloric acid and carbon dioxide corrosion.The main conclusions of the thesis are as follows:(1)Based on the hydrochloric acid corrosion in oilfield acidification operations,a series of organic molecules with corrosion inhibition effects are synthesized.The synthetic organic molecules show excellent inhibition ability to hydrochloric acid corrosion.Based on the evaluation results,a corrosion inhibitor formulation that can effectively inhibit acid corrosion is proposed through optimization and compounding process.Varieties of steel materials have been used to conduct dynamic corrosion evaluation on the formulations,and the formulation shows excellent corrosion inhibition performance with all materials(annual corrosion rate less than 5 mm/a,the minimum rate is 3.52 mm/a).(2)The mechanism of the synthetic hydrochloric acid corrosion inhibitor has been defined.The synthesized product can form a monomolecular layer mixed adsorption on the metal surface,change the surface affinity and hydrophobicity,and reduce the corrosion damage of the metal surface.Molecular simulation calculations are performed,the influence of molecular structure on corrosion inhibition performance is studied,and the reason for the difference between the theoretical calculation and the experimental phenomenon is explained.The length of the molecular alkyl chain has an impact on the corrosion inhibition effect,and the optimal length range of the alkyl chain can be confirmed by simulation calculation.Properties such as protonation and dispersion are important reasons for the differences between calculations and experiments.In the process of corrosion inhibitor research,in addition to the theoretical calculation results,it is necessary to fully consider the similar properties of organic molecules.(3)Based on biomaterials like chitosan and chitosan oligosaccharides,a series of macromolecular Schiff bases are synthesized.The inhibition efficiency of products exceeds 90%in carbon dioxide saturated solution containing 3.6%wt.Na Cl at 80℃.Based on evaluation results,a high-temperature carbon dioxide-resistant green corrosion inhibitor formula is formulated.The dynamic carbon dioxide corrosion evaluation experiment is carried out in simulated formation water with salinity of 2.4×10~5 mg/L at140℃:For all types of steel tested,the formula can control the corrosion rate to less than0.076 mm/a(the minimum rate is 0.049 mm/a),which meets the requirements of corrosion protection.Corrosion inhibitors synthesized based on biological macromolecules are non-toxic and pollution-free,meet the requirements of green chemistry,and have good corrosion inhibition effects,which can effectively inhibit the corrosion damage caused by carbon dioxide.(4)Theoretical calculation and mechanism of synthetic corrosion inhibitors are carried out,and the interaction between synthetic molecules and the metal surface is characterized:SEM and AFM confirm that the corrosion inhibitor affects the change of the surface micro morphology through adsorption and reduces the formation of corrosion products.The adsorption behavior follows Langmuir monolayer adsorption.Through contact angle,it is established that the adsorption makes the metal surface a hydrophobic surface,reducing the contact with corrosive media.In addition,simulation calculations are carried out on the organic structure.According to the calculation results of the front-line orbital parameters and reactive sites of organic molecules,it is verified that the modification can enhance the electrophilicity of the molecules,strengthen the electron exchange between organic molecules and metal atoms,and enhance the corrosion inhibition performance.At the same time,the benzene ring substituent can provideπelectrons and more active sites for adsorption,and the effect of enhancing the corrosion inhibition performance of the molecule is stronger.