Materials Performance

NOV 2018

Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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34 NOVEMBER 2018 W W W.MATERIALSPERFORMANCE.COM CHEMICAL TREATMENT Corrosion Effects of Impurities in EOR and Geological Storage Processes When the CO 2 mixtures are injected through the injection well, corrosion will not be a major problem based on the dry-out effect during the injection process. However, the presence of acid gases and formation water can cause the formation of strong acids, which will lead to severe corrosion on the well infrastructures, particularly on the production well. The corrosion phenome- non in production wells is complex, with impurities from the injected CO 2 mixtures and mineral ions in the formation water mixed in the multiphase with crude oil, gas, water, and solid particles at the high-tem- perature, high-pressure conditions. In 2015, there was a casing material fail- ure accident in an oil field in China using CO 2 mixtures as the EOR displacement gas, and the failure analysis results showed that there was 30 to 40 ppmv H 2 S impurity in the CO 2 source, leading to sulfide stress crack- ing (SSC). 12 Acidic gases can have chemical effects on the rocks. SO x can react with rocks to form sulfate that can be deposited, reduce rock porosity, and eventually diminish injectivity. W h en S O 2 and H 2 S are co- sequestered, the deposition of elemental sulfur may also reduce injectivity. Nogueira and Mamora 13 concluded that injection with no more than 1 mol% impurities would result in practically the same volume of CO 2 being stored as injecting pure CO 2 , but it would have a lower separation cost compared to an extremely high-purity CO 2 scenario. The separation of CO 2 and other impu- rities with oil production is costly, and the impurities may also influence downstream production. For example, O 2 could promote th e grow th of a erobic bacteria , w hich induces biodegradation of crude oil and adversely affects oil recovery and refine- ment. 14 This may also induce the microbio- logically influenced corrosion. When the injection process is termi- nated , the corrosion of well steels and cements will be problematic owing to the loss of the desiccation effect of the well zone during the injection process. The well integrity under long-term exposure might be a real challenge for the permanent geo- logical storage of CO 2 . The leakage of CO 2 from the wells is a major concern for the CCUS technology. General Discussion To control the corrosion problems of steels in CCUS systems, the utilization of inhibitors could be an economical and effective method, besides the application of corrosion-resistant alloys, coatings, and cathodic protection. However, when vari- ous acid gases are present, it seems to be hard to find inhibitors that can reduce the corrosion rates of steels under the attack of both strong and weak acids, including sul- furic acid (H 2 S O 4 ), nitric acid (HNO 3 ), H 2 SO 3 , carbonic acid (H 2 CO 3 ), and H 2 S. Recently, it was reported that piperazine can neutralize the acidic gas impurities and inhibit the corrosion of CS in super- critical CO 2 -saturated aqueous phases con- taining SO 2 , nitrogen dioxide (NO 2 ), and O 2 impurities. 15 Piperazine and its derivatives are potential inhibitors of steel corrosion in CCUS environments. Meanwhile, control- ling the water content in the CO 2 streams can be an alternative corrosion control strategy. The safety of CCUS is one of the most important issues that impede its large- scal e appli cation s. Alth ou g h a ci d ga s impurities have a dissolution effect on cap- ro ck s, a se c ond-phase d e p o sition can increase the porosity as well as enhance the safety of CCUS. At geological fault loca- tions, seismic activity and/or failure of well integrity could be a huge threat to CCUS safety, which can result in a fast leakage of sequestered CO 2 to the earth surface and seriously pose risks to the safety of human beings. However, it is not probable that seismic activity is a problem at all CO 2 stor- age sites at the same time. Nevertheless, there is a great necessity to choose CO 2 storage sit es far away from populat ed regions. The well integrity and the impact of potential activity resulting from CO 2 storage are the greatest threat to CCUS safety. Acknowledgments The author would like to acknowledge that this work was financially supported by National Key R&D Program of China (2017YFC0805800), National Natural Sci- ence Found ation of China (51604289), B e i j i n g N a t u r a l S c i e n c e Fo u n d a t i o n (2172048), and S ci en c e Found ation of China University of Petroleum , Beijing (2462014YJRC043). References 1 H.J. Liu, P. Were, Q. Li, et al., "Worldwide Sta- tus of CCUS Technologies and their Develop- ment and Challenges in China," Geof luids 2017, pp. 1-25. 2 Y. Xiang, M. Xu, Y.-S. Choi, "State-of-the-Art Overview of Pipeline Steel Corrosion in Im- pure Dense CO 2 for CCS Transportation : Mechanisms and Models," Corros. Eng. Sci . Techn. 52, 7 (2017): pp. 485-509. 3 Y. Hua, R. Barker, A. Neville, "Understanding the Influence of SO 2 and O 2 on the Corrosion of Carbon Steel in Water-Saturated Super- critical CO 2 ," Corrosion 71, 5 (2015): pp. 667- 683. 4 L. Wei, X. Pang, K. Gao, "Corrosion of Low Alloy Steel and Stainless Steel in Supercriti- cal CO 2 /H 2 O/H 2 S Systems," Corros. Sci . 111 (2016): pp. 637-648. 5 M. Xu, Q. Zhang, Z. Wang, et al., "Effect of High-Concentration O 2 on Corrosion Behav- ior of X70 Steel in Water-Containing Super- critical CO 2 with SO 2 ," Corrosion 73, 3 (2017): pp. 290-302. 6 J.J. Taber, "Fate of Small Concentrations of SO 2 , NO x and O 2 When Injected with CO 2 into O i l R e s e r v o i r s" ( L e m o n t , I L : Arg o n n e National Laboratories, 1985). 7 Y. Xiang, Y.-S. Choi, Y. Yang, et al., "Corrosion of Carbon Steel in MDEA-Based CO 2 Capture P l a n t s Un d e r R e ge n e ra t o r C o n dit i o n s : Effects of O 2 and Heat-Stable Salts," Corrosion 71, 1 (2015): pp. 30-37. 8 L. Zheng, J. Landon, N.S. Matin, et al., "FeCO 3 Coating Process Toward the Corrosion Pro- tection of Carbon Steel in a Postcombustion CO 2 Capture System," Ind. & Eng. Chem. Res. 55, 14 (2016): pp. 3,939-3,948. 9 Y. Xiang, C. Li, Z. Long, et al., "Electrochemi- cal Behavior of Valve Steel in a CO 2 /Sulfurous Acid Solution," Electrochim. Acta 258 (2017): pp. 909-918. 10 V.E. Onyebuchi, A. Kolios, D.P. Hanak, et al., "A Systematic Review of Key Challenges of CO 2 Transport via Pipelines," Renew. Sust. Energ. Rev. 81, Part 2 (2018): pp. 2,563-2,583. 11 C. Sun, J. Sun, Y. Wang, et al., "Effect of Impu- rity Interaction on the Corrosion Film Char- acteristics and Corrosion Morphology Evolu- tion of X65 Steel in Water-Saturated Super- critical CO 2 System," Int. J. Greenh. Gas Con. 65, Supplement C (2017): pp. 117-127. 12 X. Zhao, Z. He, J. Liu, et al., "Research Status of CCUS Corrosion Control Technolog y," Petrol. Tubular Goods & Instrum. 3, 3 (2017): pp. 1-6.

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