Corrosion behavior of 13Cr casing steel in cement-synthetic pore solution exposed to high pressure CO2 and H2S

The electrochemical corrosion behavior of grade L-80, type 13Cr casing steel was investigated in cement-synthetic pore solution (CSPS) exposed to CO2 and H2S using in-situ electrochemical methods and ex-situ surface analyses at 85 and 200 °C, respectively. Total system pressure was 10 MPa. Corrosion rates increased significantly when the temperature increased from 85 to 200 °C. Limiting current behavior was observed for the anode reaction, while charge-transfer control was observed for the cathode reaction. Surface analyses revealed the presence of CaCO3 on the surface at both temperatures and FeCO3-like deposits at 200 °C

Effects of CO2 and H2S on corrosion of martensitic steels in brines at low temperature

Corrosion studies were conducted for martensitic carbon steels in 5 wt% NaCl brine solutions at 4°C and 10 MPa (1,450 psi). These studies simulated different subsurface environments relevant to Arctic drilling. Here, two high-strength martensitic carbon steels, S-135 and UD-165, were studied in three different environments: (1) a CO2-NaCl-H2O solution with a CO2:H2O molar ratio of 0.312 in the whole system, (2) an H2SNaCl- H2O solution with an H2S:H2O molar ratio of 3.12 × 10−4, and (3) a CO2-H2S-NaCl-H2O solution with the same acid gas to water ratios as environments 1 and 2. Results from the CO2+H2S mixed environment indicated that sour corrosion mechanism was dominant when the CO2:H2S molar ratio was 1,000. This impact of a small amount of H2S on the corrosion mechanism could be attributed to the specific adsorption of H2S on the steel surface. Electrochemical and mass loss measurements showed a distinct drop in the corrosion rate (CR) by more than one order of magnitude when transitioning from sweet to sour corrosion. This inhibiting effect on CR was attributed to the formation of a protective sulfide thin film

Thermodynamic stability analysis of the carbon biogeochemical cycle in aquatic shallow environments

We carry out the thermodynamic stability analysis of the carbon cycle in a lagoon. Our approach differs from linear stability analysis, and is based on the excess entropy production. The coupled biogeochemical processes in the lagoon include gas transfer, photosynthesis, respiration, decomposition, sedimentation, and oxidation of algae. The thermodynamic stability criterion derived from this analysis indicates that, in addition to known limiting factors of biomass production such as temperature, light, and nitrogen and phosphorous concentrations, the rate of carbon dioxide delivery from the air reservoir to the water can be also a limiting factor. For the Venice lagoon, the criterion obtained predicts that a doubling of the CO2 partial pressure in the atmosphere can render the system unstable, driving it to dramatic biomass production and degradation

Potentiometric pH measurements in acidic sulfate solutions at 250 °C relevant to pressure leaching

A flow-through yttria-stabilized zirconia (FTYSZ) electrode has been employed for pH measurements at 250 °C in concentrated electrolyte systems relevant to hydrometallurgical processing of nickeliferous laterites. Experiments were conducted using a custom-made flow-through titanium electrochemical cell specially designed for high-temperature potentiometric pH measurements. In the present work, we assess the accuracy and validity of pH measurements with theory at 250 °C on concentrated sulfate process solutions. First, binary sulfuric acid–water solutions were measured at concentrations ranging from 0.05 to 0.5 mol kg −1 and showed 0.3 pH unit increase on the average between 25 and 250 °C. The measurements were then extended to ternary and quaternary systems containing 0.0076–0.038m Al 2(SO 4) 3 and 0.0276–0.276m MgSO 4, respectively. Autoclave passivation against corrosion was successfully achieved using sodium chromate or hydrogen peroxide. In this technique, the potentials are measured against a Ag/AgCl flow-through external reference electrode (FTEFE). A reference solution of 0.1 mol kg −1 NaCl(aq) flows permanently through the electrode at a constant flow rate, so that the thermal liquid junction and streaming potentials are kept constant. The experimental results were compared with theory using available thermodynamic data for estimating the quality of pH measurements. An average difference of 0.15 pH unit was observed between measured and theoretical values at temperature

Reference systems for assessing viability and accuracy of pH sensors in high temperature subcritical and supercritical aqueous solutions

This paper describes an effort in developing reference systems to be used in high temperature subcritical and supercritical aqueous solutions for assessing the viability and accuracy of high-temperature pH sensors. Each of these reference systems consists of a couple of three-component aqueous solutions in which the concentration of NaCl is greater than the concentration of another solute, such as HCl and NaOH. The viability of the reference systems was tested using the recently published experimental data employing a flow-through electrochemical cell at temperatures from 25°C to 400°C and densities from 0.17 to 1 g cm −3 [S.N. Lvov, X.Y. Zhou, and A.V. Bandura, 1999a, Estimation of Isothermal Potential for HCl/NaCl and NaOH/NaCl Systems in High Temperatures Supercritical Aqueous Solutions, J. Supercrit. Fluids, in preparation; S.N. Lvov, X.Y. Zhou, and D.D. Macdonald, 1999, Flow-Through Electrochemical Cell for Accurate pH Measurements at Temperature up to 400°C, J. Electroanal. Chem., 463, 146–156]. The applicability of the method was tested for dilute (0.01 and 0.001 mol kg −1) HCl aqueous solutions having background NaCl electrolyte in the amount of 0.1 mol kg −1. The most significant property of the reference systems is that the pH difference, and hence, the cell potential, can easily be estimated with sufficient accuracy using only the analytical concentrations of the electrolytes without considering the speciation calculations, given the fact that the association and dissociation constants at supercritical temperatures have not been accurately determined yet

Quantitative evaluation of general corrosion of Type 304 stainless steel in subcritical and supercritical aqueous solutions via electrochemical noise analysis

Electrochemical noise (EN) sensors have been developed to measure the corrosion rate of Type 304 stainless steel ( SS) in subcritical and supercritical environments. The EN sensors were tested in flowing aqueous solutions containing NaCl and HCl at temperatures from 150°C to 390°C, a pressure of 25 MPa, and flow rates from 0.375 to 1.00 ml/min. The potential and coupling current noise were recorded simultaneously and the noise resistance ( R n) was calculated from the standard deviations in the potential and current records. We found that the inverse noise resistance correlated very well with the corrosion rate evaluated from separate mass loss experiments, and that both the inverse noise resistance and the average corrosion rate were functions of temperature and flow rate. In the temperature range from 200°C to 390°C, the corrosion rate was found to be proportional to the inverse noise resistance and hence the Stern–Geary relationship can be used to evaluate the corrosion rate. However, at 150°C, the relation between inverse noise resistance and corrosion rate significantly deviated from the Stern–Geary relationship. It was found that the deviation was related to the low corrosion rate of Type 304 SS and 150°C

Digitization of Economic Space as an Imperative for the Formation of a Knowledge Economy

Currently, information and communication technologies play a huge role not only in the lives of individuals, but also transform economic processes, modernize entire industries and various types of social and economic activity, and become drivers of innovation, economic growth and competition. The purpose of this study is to show how digital technologies modify the economic space and thereby influence the formation of the knowledge economy. The article defines the “knowledge economy”, shows the stages of its formation. The authors argue that digital technologies will be the basis for the development of the knowledge economy in the coming years. At the second stage, an important role will be played by the intellect, creative abilities of a person, aimed at creating innovations. © Springer Nature Switzerland AG 2020

Effects of H2S and CO2 on Cement/Casing interface corrosion integrity for cold climate oil and gas well applications

Low-temperature corrosion relevant to oil and gas wells was investigated. Casing cement was exposed to brine in contact with CO2 at 4 °C and 10 MPa. Pore water was extracted from wet cement using a die press, and a cement simulated pore solution (CSPS) was developed to be used for corrosion studies. High levels of chloride similar to the original brine solution were found. The sodium content was well below that of the original brine, with the change in charge mostly balanced by an increase in dissolved calcium. The calcium content was above predictions for brine-CO2- Ca(OH)2 equilibrium, suggesting that sodium was displaced in favor of calcium. Corrosion measurements were performed on casing steel using linear polarization resistance, electrochemical impedance spectroscopy, and mass loss samples with H2S:CO2 ratios from 0 to 0.001. The corrosion rate was found to decrease slightly with increasing sulfide content from 0.02 to 0.01 mm y-1