CO2-saturated Formation Water Research Articles

Temperature and Reaction Time’s Effects on N80 Steel Corrosion Behavior in Supercritical CO2 and Formation Water Environments

In the present study, an immersion experiment was carried out to examine how N80 steel corrodes when exposed to formation water containing dissolved CO2 and supercritical CO2 (Sc-CO2) along with water vapor. We employed electrochemical and surface analysis methods to examine the influence of various factors, including the temperature and duration of immersion, on the extent of corrosion. The results show that the corrosion patterns of N80 steel in a supercritical CO2 environment and CO2-saturated formation water differed significantly. The presence of similar corrosion features was suggested by the constant structure of the corrosion products identified in the formation water. However, the morphology of the corrosion product was complex in the supercritical CO2 environment, exhibiting features of pitting and localized corrosion. Furthermore, a non-linear trend in the corrosion rate was observed between 40 °C and 120 °C. Specifically, the rate of corrosion declined from 40 °C to 80 °C, but it then resumed its growth from 80 °C to 120 °C. These findings suggest that very high temperatures could lead to the destruction of corrosion products and subsequently enhance the corrosion process.

Study of furfural derivatives as a possible green corrosion inhibitor for mild steel in CO2-saturated formation water

The anticorrosive activity of furfural derivatives, by ex-situ and in-situ syntheses, on mild steel immersed in CO2-saturated formation water solution was evaluated using mass loss measurements, polarization curves, X-ray photoelectron spectroscopy, quantum chemical calculation, and electrochemical impedance. Furfural thiosemicarbazone presented inhibition efficiency reaching 90.2% for 72 h in immersion. The same molecule, synthesized in-situ by the mixture of the precursors in the corrosive medium, also produced good efficiency, 82.2% for 24 h of immersion, but it decreased over the time due to incomplete conversion of the precursors in furfural thiosemicarbazone.

Pectin-amino acid derivatives as highly efficient green inhibitors for the corrosion of N80 steel in CO2-saturated formation water

Pectin, as the raw material from the waste peel and residue of various plants, was applied to prepare an environmentally friendly, inexpensive, and biodegradable green modified-pectin (P-Gly and P-Lys) corrosion inhibitor. Elemental analysis, FTIR spectroscopy, 1H NMR and XRD analysis confirmed the grafting degrees of amidated pectin were 6.26% (P-Gly) and 7.20% (P-Lys), respectively. The corrosion inhibition mechanism of P-AAs on N80 carbon steel in CO2-saturated groundwater was investigated. It was found that P-AAs showed high corrosion inhibition efficiencies at a low concentration of 800 mg/L: P-Gly (99.01%) and P-Lys (99.36%) with excellent adsorption stability maintained for 120 h. Theoretical calculations including QC based on DFT and GFN-xTB methods and MD-based RDFs revealed the chemisorption of the inhibitors on the Fe surface.

In-depth insight into the inhibition mechanism of the modified and combined amino acids corrosion inhibitors: “intramolecular synergism” vs. “intermolecular synergism”

In this work, amino acid (L-histidine (LHD)) and 1-phenylthiourea (PT) were mixed as the combined corrosion inhibitors (LHD + PT). Meanwhile, LHD was also modified with phenyl isothiocyanate to develop a novel corrosion inhibitor (phenylcarbamothioyl)histidine (PT-HD), which has a combined structure of LHD and PT. Then LHD + PT is the “intermolecular synergism”, while PT-HD could be regarded as the “intramolecular synergism” of LHD and PT. The inhibition performances of LHD + PT and PT-HD for the corrosion of carbon steel in CO2-saturated formation water were investigated by electrochemical tests and surface analyses. Additionally, the intrinsic difference in the inhibition performance and mechanism of LHD + PT and PT-HD were in-depth revealed by theoretical calculations. The experimental results indicate that PT-HD exhibits better inhibition performance than LHD + PT (inhibition efficiency of 99.2% for 0.4 mM LHD + PT and 99.3% for 0.4 mM PT-HD), i.e., the “intramolecular synergistic inhibition effect” is stronger than the “intermolecular synergistic inhibition effect”. The theoretical calculations also indicate that PT-HD has stronger adsorption ability and more effective prevention to the invasion of aggressive species. The higher inhibition efficiency of PT-HD is associated with the fact that the LHD and PT fragments in PT-HD molecule are closely linked by chemical bond, forming a more compact adsorbed inhibitor film on steel surface.

Mercaptopropionic acid-modified oleic imidazoline as a highly efficient corrosion inhibitor for carbon steel in CO2-saturated formation water

Two imidazoline derivatives (OI and MOI) were synthesized as highly efficient inhibitors, and their inhibition performances and mechanisms in CO2-containing solution were studied using weight loss measurements, electrochemical tests, surface analysis and theoretical calculations. The results indicate that OI and MOI show excellent inhibition efficiency. Especially for MOI, its inhibition efficiency is as high as 95.58% at 20 ppm. Theoretical calculations confirm that both inhibitors successfully adsorb on metal surface via chemisorption. MOI shows a better inhibition performance than OI, because the sulfhydryl in MOI can be used as a powerful adsorption site, effectively improving the adsorption ability of MOI.

Two amino acid derivatives as high efficient green inhibitors for the corrosion of carbon steel in CO2-saturated formation water

Amino acids are the promising biomolecules as eco-friendly inhibitors for the corrosion protection of materials. In this work, two amino acid derivatives (MPT and BPT) were synthesized as green inhibitors, and their corrosion inhibition performance for N80 carbon steel in CO2-saturated formation water was studied by electrochemical tests and surface analysis. It is found that both MPT and BPT exhibit outstanding inhibitive effect (inhibition efficiency of 99.26 % for MPT and 99.44 % for BPT), which is significantly higher than those already reported amino acid derivative inhibitors. The inhibition mechanism of MPT and BPT was also revealed by theoretical calculations.

Mineral dissolution and precipitation reactions and their net balance controlled by mineral surface area: An experimental study on the interactions between continental flood basalts and CO2-saturated water at 80 bars and 60 °C

Continental flood basalts are currently considered as unconventional CO2 storage reservoirs given several knowledge gaps remain. This study addresses the question whether subvertical fractures and joints in the storage complex and its overburden may lead to long-term CO2 leakage or whether commencement of self-sealing can be expected at an early stage of geochemical reactions. The latter occurs when mineral precipitation outcompetes mineral dissolution. The nature of secondary mineral precipitation and the change of ion concentrations over time were studied in a batch reactor experiment where basalt wafers with a low surface area were exposed to CO2-saturated formation water at a pressure of 80 bars and 60 °C. Primarily stilbite (a zeolite) and montmorillionite (a smectite) were observed in suspension and kaolinite, Fe-oxide and Na-nontronite were additionally identified as authigenic minerals on the surface of the basalt wafers at the end of the incubation. These observations are in agreement with the state of mineral saturation based on the water composition throughout the incubation. Carbonate minerals were undersaturated throughout the incubation suggesting limited carbon mineral trapping capacity under the given conditions. A mineral nucleation phase (day 1 to 6) dominated by cation release due to dissolution and a mineral growth phase (day 8 to 44) dominated by cation uptake due to precipitation were identified. The latter resulted in the formation of considerable mineral mass, which was deposited almost completely on the wafer surface.

Evolution and characterization of the film formed on super 13Cr stainless steel in CO2-saturated formation water at high temperature

The evolution and characterization of films formed on super 13Cr at 90 °C and 200 °C were investigated by Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), X-Ray Photoelectron Spectroscopy (XPS), Focus Ion Beam (FIB) and Transmission Electron Microscopy (TEM) and localized Raman spectroscopy. The results show that super 13Cr maintains a passive state at 90 °C, while an active state exists with a high corrosion rate of 0.43 mm/year at 200 °C for the first 5 h, then stabilizes to a rate of 0.125 mm/year over 5 days exposure. The passive film formed at 90 °C is an amorphous-like structure with high Cr content, while the corrosion product films formed at 200 °C are mainly comprised of nanocrystalline spinel FeCr2O4 and crystalline FeCO3.

Understanding the influences of temperature and microstructure on localized corrosion of subsea pipeline weldment using an integrated multi-electrode array

The localized corrosion behaviour of an X65 subsea pipeline weldment in CO2-saturated formation water was studied using weldment coupon and a novelly designed weldment multi-electrode array (WMEA). The dynamic progression of localized corrosion on different welding areas i.e. base metal (BM), heat affected zone (HAZ) and welding metal (WM) was probed by WMEA. The influences of the solution temperature and the steel microstructure on the localized corrosion of subsea pipeline weldment were analysed. The test results show that HAZ and WM would act as anodes registering a high corrosion rate which was controlled by both micro-cell corrosion and macro-cell corrosion below 50 °C. While, if the temperature increased higher than 50 °C, WM would transfer from major anode to significant cathode due to the preferential deposition of FeCO3 crystal on WM. Part areas of HAZ would act as the main anodic sites and maintain a high local anodic dissolution rate due to the macro-cell current which is induced by the inhomogeneous FeCO3 film covering.

Microbiologically Influenced Corrosion of Carbon Steel Beneath a Deposit in CO2-Saturated Formation Water Containing Desulfotomaculum nigrificans.

The corrosion mechanism of carbon steel under deposit in the presence of sulfate reducing bacterium (SRB) Desulfotomaculum nigrificans was studied using surface analysis, weight loss and electrochemical measurements. Results showed that both the general corrosion and localized corrosion were considerably promoted by SRB under deposit. The corrosion rate of steel in the presence of SRB was approximately 6 times of that for the control according to the weight loss measurements. The maximum corrosion pit depth in the presence of SRB was approximately 7.7 times of that of the control. Both the anodic and cathodic reactions were significantly accelerated by SRB. A galvanic effect in the presence of SRB due to the heterogeneous biofilm led to serious localized corrosion.

Effect of temperature on corrosion behaviour of N80 steel in CO2-saturated formation water

Corrosion behaviour of N80 steel in CO2-saturated format ion water was studied by weight loss measurement, electrochemical test and surface characterization. The results showed that the general corrosion rate init ially increased and decreased with the increase of temperature and it reached maximum at 60 °C about 10 mm/y. The polarization curves showed the similar results on corrosion rate of N80 steel after the exposure experiment in CO2-saturated format ion water. Localized corrosion was observed at the temperature of 40 °C and 50 °C. The XRD pattern indicated that the corrosion product was mainly composed by Fe3C when the temperature under 50°C, then FeCO3 appeared when the temperature was above 50 °C. At 70 °C, the corrosion product was comprised of FeCO3 totally. Generally, the temperature of 60 °C was the turning point for corrosion type and corrosion product transformation in the test conditions.

Characterization of corrosion scale formed on 3Cr steel in CO2-saturated formation water

The evolution of the corrosion scale formed on 3Cr steel was investigated by scanning electron microscopy (SEM) and X-Ray Diffraction (XRD). The inner layer was characterized by Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Thermogravimetric analysis-differential scanning calorimetry (TG-DSC). The results show the inner layer is an amorphous-like structure containing some nano-quasicrystalline and nanocrystalline grains which is more uniform and less porous than the crystalline FeCO3 layer. At the 2nd stage, the transition of cathodic reactions was found, and the growth of the FeCO3 phase in the inner layer dramatically decreased the film porosity, resulting in the passivation.

Corrosion of Cr bearing low alloy pipeline steel in CO2 environment at static and flowing conditions

We study the corrosion performance of Cr bearing low alloy pipeline steel (Cr3MoNi) in CO2 saturated formation water, under both static and flowing conditions. Cross-sectional morphologies of corrosion scales at progressively increased test duration are observed by scanning electron microscopy. The characteristic of the corrosion scales are investigated by energy dispersive X-ray spectroscopy and X-ray diffraction. Our results show that the corrosion rate of Cr3MoNi steel at flowing condition is higher than that of static condition, and the degree of Cr enrichment in the scales at flowing condition is also higher. Flow also makes ions distribute evenly in the solution close to the specimen, leading to a uniform distribution of Cr compound in the amorphous corrosion scales. In this way, flow suppresses the presence of the potential pits and also leads to a more flat scale/substrate interface.

Corrosion of X65 steel in CO 2-saturated oilfield formation water in the absence and presence of acetic acid

Electrochemical corrosion behavior of X65 steel in CO 2-saturated formation water in the absence and presence of acetic acid was studied by electrochemical measurements, scanning vibrating micro-electrode (SVME), localized electrochemical impedance spectroscope (LEIS) and surface analysis techniques. It is found that, when steel is immersed in formation water, the dissolution of Fe dominates the anodic process and the steel is in active dissolution state. Adsorption of intermediate product on the electrode surface results in generation of an inductive loop in the low frequency range of EIS plot. As corrosion proceeds, the concentration of Fe 2+ in the solution increases. When the product of [Fe 2+] × [ CO 3 2 - ] exceeds solubility product of FeCO 3, FeCO 3 will deposit on the electrode surface, and protects the steel substrate from further corrosion. The steel is in a “passive” state. When the electrode surface is completely covered with FeCO 3 film, the inductive loop in the low frequency range disappears. In the presence of acetic acid in formation water, the cathodic reaction will be enhanced due to the direct reduction of undissociated acetic acid. Addition of acetic acid degrades the protectiveness of corrosion scale, and thus, enhances corrosion of steel by decreasing the FeCO 3 supersaturation in solution.