Gazovaya promyshlennost’ № 05 2022

The article presents the data on how different microstructures affect the CO2 corrosion rate of tubing made of low-carbon manganese steels. Corrosion protection under such conditions requires inhibitors or replacing items with those made of corrosion-resistant materials. The chemical composition and microstructure type of carbon steels can affect the resistance to СО2 corrosion. To prove this statement, tubing metal specimens were examined according to the current standards. It was found that the ferritic-pearlitic microstructure is formed during heat treatment of steels and results from equilibrium austenite decomposition at slow cooling. Such microstructure significantly reduces the carbon dioxide corrosion rate compared with the secondary sorbite microstructure due to dissolution of the ferrite and retaining of the laminated pearlite. Thus, the corrosion rate of steel with ferritic-pearlitic microstructure was 5.3 times lower than that of the secondary sorbite microstructure steel. However, the latter has better strength properties than the ferritic-pearlitic steel. Secondary sorbite has an acicular structure that gives high tensile strength results in mechanical testing. The trade-off between corrosion resistance and strength properties should be resolved to use manganese steels as a high-tensile tubing material in СО2 environments.

This article continues the authors’ previous works on the application of interferometric synthetic aperture radar (InSAR) techniques to oil and gas applications. This publication offers the additional practical applications of this technology. The capabilities of the method for monitoring underground gas storage facilities, CO2 assembly and disposal, and offshore field development are described. The article shows that InSAR data processing is one of the most promising and cost-effective methods capable of providing high accuracy and sufficient spatial density of the displacement vector field of the day surface. This allows the technology to be used in the monitoring of underground gas storage facilities. In offshore field development the InSAR method finds its application in multiplatform analysis performed for a group of drilling platforms and in measuring deformations of offshore structures. It is noted that the use of the described technology can generally improve the reliability of geological process forecasting.

Investment decision-making in the gas industry is associated with analyzing integrated investment projects that comprise multiple subprojects within adjacent business lines. That being said, PJSC Gazprom has different requirements for the return on investment for different business lines, which has to be considered when setting corporate requirements for the integrated project return. The required return figures for the integrated project and its subprojects shall be aligned to rule out any inconsistent conclusions resulting from investment analysis. Thus, an urgent practical objective for investment economic evaluation in the gas industry is to substantiate a correct method for determining the required return of an integrated investment project. The conventional approach to determining the required return for multiple simultaneous projects has long been known in the financial investment portfolio management theory and is widely used in practice. However, transferring it into a real sector of the economy without a proper adaptation might result in incorrect decisions. The article uses a calculation example to demonstrate the downsides of the conventional method for determining the required return on investment in an integrated project. A new approach is proposed for the first time as an alternative. It is based on calculating investment values and tariffs by subprojects and ensures one-to-one correspondence of the economic evaluations of the integrated project and its subprojects. Thus, the new approach reduces the risk of incorrect investment decisions compared with the conventional method. The article mathematically proves that the required return for an integrated project determined using investment values and tariffs by subprojects is only achieved when the return requirements for each subproject are met. The new method’s applicability is also illustrated by the respective calculation of the economic efficiency indicators of the integrated project and its subprojects.

The article presents a methodological approach to the quantitative risk assessment for a large international vertically integrated company using the VaR (value at risk) historical simulation method. The main objective of the approach is to build a formalized algorithm for quantitative assessment (short-term forecasting) of the market (currency, interest rate, stock, price) risks by subsidiaries of the parent company. The article consists of two parts. The first one describes the theoretical basis of the quantitative risk assessment using the VaR historical simulation method. The second part provides the calculation algorithms according to this method: parametric and non-parametric. Their description is accompanied by examples of the Brent crude oil price forecasting, an indicator of market price (commodity) risk. It is concluded that the proposed methodological approach based on the use of the VaR historical simulation method can be used by risk owners (co-owners) and risk coordinators of oil and gas company organizations when assessing indicators of currency, interest, market, and other types of risks.

Main pipelines are exposed to loads and corrosion during operation. It is therefore important to ensure their operability under loading conditions, including bending loads, in the defected metal loss areas formed via corrosion mechanism. This is where the stress and strain concentrate, reducing the safety margin of a pipeline. The article discusses physical and computer experiments aimed to determine the stress-strain state of a pipe in metal loss areas under bending load. The research subject was a pipe with the following parameters: outside diameter 114 mm, wall thickness 4.5 mm, length 1 m, steel grade St3sp, yield strength 250 MPa, tensile strength 460 MPa. The upper, lateral, and lower elements of the pipe had metal loss defects with geometric centers located at 100 mm from the pipe center. The defects were 50 mm long and 30 mm wide, with maximum depths of 0.5; 1.0; 1.5; 2.0; 2.5; 3.0 mm and rectangular longitudinal sections. We also determined the stress-strain state of the pipe’s defect-free areas. The physical experiment was performed on a laboratory bench using full-scale specimens of pipes with artificial defects. The experiment included the measurements of the hoop, longitudinal strains, and strains at an angle of 45° to the pipe axis in each defect under bending load. Further, we calculated the hoop and longitudinal stresses (using the elastic deformation formulas) and the equivalent von Mises stresses and found the dependence of stresses and strains on the depth of metal loss defects. The computer experiment was performed in the Ansys software package, simulating a pipe with the same geometry, size, and defect locations as in the physical experiment. The material (structural steel) and its mechanical characteristics were also the same. We compared the equivalent von Mises stresses obtained in the two experiment types: the resulting deviation does not exceed 17.3%.

In this article, the processes of filling warm and cold tanks with vapor discharge (two-line filling scheme) and with closed drainage (single-line filling scheme) are discussed. An analysis of the previous works in the area under consideration shows that the computational models are divided into models based on the assumption of the equilibrium coexistence of phases in the reservoir being filled, and models partially taking into account phase separation. As a rule in the existing equilibrium models the energy conservation equation for an open thermodynamic system is replaced by approximate relations that simplify the analytical notation by approximating the internal energy through differential relations in temperature, pressure, and mass. This approximation does not allow the use of the computational models for multicomponent mixtures, which include liquefied natural gas. The paper presents a system of computational equations obtained on the basis of the equilibrium approximation, which makes it possible to take into account the effect of the component composition of the charged cryogenic product. The features and results of computational equations’ system’s application are considered. As a development of non-equilibrium models, the authors proposed a two-layer model with the division of the tank volume into two equilibrium layers with a predominant vapor content and a predominant liquid content. The simulation results for the proposed two-layer model, taking into account the accepted assumptions, are in good agreement with the experimental data obtained by Gazprom VNIIGAZ LLC and allow considering the processes of filling cryogenic on-board fuel systems not only with pure substances, but also with multicomponent mixtures.

The reliability of long-term operated main gas pipelines is ensured by their timely technical diagnostics, the results of which reveal deviations from regulatory requirements, including those ones in terms of the level of the stress-strain state of the pipe wall. Based on the analysis of regulatory requirements related to the design (SP 36.13330.2012) and construction (SP 86.13330.2014) of main gas pipelines, it is shown that recommendations for calculating the total longitudinal stresses in the pipe wall from all loads and impacts are explicitly presented only for a partial case, namely for straight and elastically curved sections in case of absence of soil subsidence and heaving. At the same time, the new possibilities of modern in-line inspection allow detecting that certain sections of long-term operated (30 years or more) main gas pipelines have bending radii significantly less than 1000Do (where Do is the outer diameter of the gas pipeline, m), which does not meet the requirements of SP 86.13330.2014. The application of SP 36.13330.2012 provisions to calculate the total longitudinal stresses in sections of main gas pipelines with a long-term operational life and bending radii of less than 1000Do creates a technically unjustified reserve in the calculations. Based on the experimental data, the article proves that in these sections of gas pipelines the level of total longitudinal stresses in the pipe wall is closely related to bending stresses.

Achimov pool gas with a high C2 + content from the Urengoyskoye oil, gas, and condensate field (Yamalo-Nenets Autonomous Okrug) is a strategically important raw material for the gas-chemical industry, particularly for the complex under construction in the Ust-Luga settlement (Leningrad Oblast). A significant concentration of fatty components in the gas can complicate its transportation via the main gas pipeline from the Nadym-Pur-Taz region. We analyzed the possibility of phase transition of high-C2 + gas at temperatures and pressures corresponding to the existing and extreme conditions in main pipelines to determine the possibility of the gaseous hydrocarbon transition to the liquid state during their pumping and the resulting loss of the valuable raw material for the gas processing complex. The sources of the liquid phase entering the gas pipeline were analyzed based on the literature and industrial experience. The phase equilibrium calculation for the Achimov pool gas from the Urengoyskoye, oil, and gas condensate field uses the Peng – Robinson equation of state and is further refined using flow simulation. It is found that the liquid phase condenses during the transportation of rich gas in the examined range of thermodynamic parameters, with the share of C3 + in the condensate reaching 94 %. The liquid mostly comprises C6 + hydrocarbons (48–87 %). The C3 + concentration in the condensed phase grows with increasing pressure and decreasing temperature. The loss in commercial gas from one shop of the comprehensive gas treatment unit with a capacity of 319,000 m3/h can reach 78.0–914.5 m3/h (gas volumetric flow rate at standard temperature (20 °С) and pressure (101,325 Pa)). Optimal gas compositions are established to minimize the possibility of gas-to-liquid transitions of hydrocarbons.