CO 2 Corrosion Behavior of High-Strength and Toughness V140 Steel for Oil Country Tubular Goods
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CO2 Corrosion Behavior of High-Strength and Toughness V140 Steel for Oil Country Tubular Goods Xiuhua Gao, Dazheng Zhang, Yong Lu, Zhongtao Fan, Linxiu Du, Guo Yuan, Chunlin Qiu, and Jian Kang Submitted: 15 August 2020 / Revised: 30 September 2020 / Accepted: 24 October 2020 / Published online: 13 November 2020 The CO2 corrosion behavior of V140 steel for oil country tubular goods exposed to high-temperature and pressure environment was studied by immersion corrosion experiments. The morphology, composition and elemental analysis of corrosion products were conducted by scanning electron microscope, x-ray diffractometer and electron probe micro-analyzer, respectively. The results showed that the corrosion rate gradually decreased and tended to be stable with the extension of corrosion time. The corrosion products in the initial stage were FeOOH and Fe2O3, and the final corrosion product was FeCO3. With the extension of corrosion time, corrosion products gradually became thick and dense from sparse. The fine and dense FeCO3 layer effectively improved the CO2 corrosion resistance of V140 steel. Keywords
carbon dioxide, corrosion behavior, high strength and toughness, oil country tubular goods (OCTG), V140 steel
1. Introduction With the increasing harsh demand of oil country tubular goods (OCTG) in deep and ultra-deep wells, ultra-high-strength OCTG require both ultra-high strength and high toughness. In addition, due to the service of OCTG in a serious and corrosive environment, it is also required to have excellent corrosion resistance (Ref 1-3), because the exploitation of H2S/CO2containing oil and gas layers in deep layers is increasing. Meanwhile, with the gradual deterioration of oil and gas exploitation conditions, the water content is getting much higher in oil and gas field. Therefore, CO2 contained in oil and gas field dissolves in water and forms carbonic acid (H2CO3). Carbonic acid is a dibasic acid, which is very corrosive to steel. At the same pH value, it is more corrosive to steel than hydrochloric acid. CO2 corrosion is an important form of corrosion for downhole oil pipes, casings and gathering pipelines in oil and gas fields (Ref 4-6). Tubing and casing strings usually withstand internal or external pressures with hundreds or even thousands of atmosphere pressures, tensile loads of several hundred tons, high-temperature and severe corrosive media. The service life of casing directly determines the life of oil wells. The safety, reliability, service life and economy of the OCTG are extremely important to the petroleum industry. With the increase in the well depth,
Xiuhua Gao, Yong Lu, Zhongtao Fan, Linxiu Du, Guo Yuan, Chunlin Qiu, and Jian Kang, State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110819, China; and Dazheng Zhang, State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110819, China; and School of Materials and Metallurgy, University of Science and Technology Liaoning, Anshan 114051, China. C
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