Surface Modification of Carbon Steel With Plasma Chemical Vapor Deposition for Enhancing Corrosion Resistance in CO2/Brine

Abstract

More and more oil and gas reservoirs are used for commercial carbon-dioxide-enhanced oil recovery (CO2-EOR), resulting in associated CO2 storage that occurs as part of the process. CO2/brine corrosion of oil tube steel that can occur anywhere along the wellbore is a challenging issue faced by the oil and gas industry. In this paper, to enhance their corrosion resistance in CO2/brine, J55 and N80 oil tube steels were coated with trimethylsilane (TMS) with the plasma chemical vapor deposition (PCVD) method. Both atmosphere and vacuum direct-current (DC) discharges were utilized for TMS plasma coatings (TMS-PCs) deposition. X-ray photoelectron spectroscopy (XPS) was used to characterize the coating surface chemistry. It was found that TMS-PCs deposited with vacuum direct current (DC) coatings (VDCPCs) had higher Si- and C-rich composition than atmospheric DC plasma coatings (ADCPCs). The corrosion resistance of samples with or without TMS-PC was evaluated through the weight loss method (WLM) and the 3-D pitting corrosion quantitative evaluation method (3D-PCQEM), which was conducted in CO2/brine with the self-built corrosion-resistant performance evaluation system (CRPES) and a 3-D scanning optical microscope. The results demonstrated that the TMS-PCs can significantly decrease not only the uniform corrosion rate but also the pitting corrosion rate of N80 and J55 oil tube steels. TMS-PCs deposited with VDCPC showed a lower corrosion rate than that of ADCPC. The scanning electron microscopy (SEM) was used to characterize the surface morphology of the samples before and after WLM, and the results indicated less corrosion and pitting corrosion on coated samples than that of uncoated controls. The energy dispersive spectrometer (EDS) was used to characterize the coating surface chemistry before and after WLM, which also indicated that the ferric content of coated samples was higher than that of uncoated controls after WLM. The results obtained in this paper indicate that TMS-PCs may serve as a very promising barrier against the corrosion and pitting corrosion of tube steel in CO2/brine.