Gazovaya promyshlennost’ № 02 2021

The demand for compositional simulation is growing in the petroleum industry. This is because this approach enables a detailed computer simulation of mass transfer processes in a reservoir fluid. On the other hand, compositional simulation requires high computational power for iterative calculation of multicomponent fluids' parameters in the thermodynamic equilibrium. The article presents an algorithm that allows for the determination of fluid parameters. This algorithm is based on direct Gibbs free energy minimization of a multicomponent system. The algorithm is compared with the standard iterative calculation algorithm by considering a set of multicomponent mixtures with known experimental parameters. The analysis has shown that the proposed algorithm does not concede the conventional one in accuracy and can demonstrate some calculation advantages in the critical region. Thus, the presented method is another independent way to verify the phase equilibrium parameters of multicomponent hydrocarbon mixtures.

The article presents modern methods for calculating gas condensate systems' thermodynamic properties, developed within the author's generalized equations of state. Two methods are based on empirical generalized multiparameter equations of state and theoretically based PC-SAFT model, respectively. The input data for the calculation is the fluid's distillation and composition. The heavy residue was modeled using the following physical and chemical properties determined by standard laboratory methods: refractive index, relative density, average molar weight, and average boiling point. The proposed methods were tested based on a literary experimental data array on the few gas condensate samples' compressibility factors. The accuracy of thermodynamic properties' description for both multiparameter and PC-SAFT equations of state turned out to be about the same. However, the latter has better prediction opportunities due to its theoretical basis. It is shown that the proposed modeling methods are quite promising for predicting thermodynamic properties of reservoir hydrocarbon fluids in a wide range of pressure-and-temperature conditions. It is also noted that the lack of reliable wide-range experimental data on the properties under research, including critical area, is the main limiting factor in improving the multiparameter model. Therefore, it is recommended to use the approach based on the PC-SAFT equation of state for poorly studied natural hydrocarbon systems.

Polyurea-based lubricating greases are quite popular today because they are biodegradable and can be further disposed of. The study uses the following esters as continuous phases to prepare biodegradable polyurea lubricating greases: dibutyl sebacate, polyethylene glycol stearate, dioctyl adipate, dioctyl sebacate, polyethylene glycol oleate, pentol, dibutyl phthalate, dioctyl terephthalate, sorbitane oleate H. The performance characteristics of polyurea lubricating greases obtained were studied separately. The results revealed some dependencies of penetration and dropping point performances on the linear size of continuous phase molecule. It was found that the penetration increases, and the dropping point decreases with the linear size increase.

The review summarizes experimental and theoretical studies by Russian scientists in gas hydrate research area. The main attention is paid to investigation of kinetics and thermodynamics of formation, growth and decomposition of gas hydrates, their properties and structure. The issues of natural gas hydrates reserves assessing, gases separation and storage using hydrate technologies, as well as related environmental problems are considered. The experimental studies of inhibiting hydrate formation are shown to be of high practical importance. Nowdays, in the Russian Federation the most relevant areas are the studies of hydrate formation in dispersed media and pore space, the elaboration of artificial obtaining methods of gas hydrates using promoters, the mathematical modeling of listed processes and the processes related to the hydrate formation prevention in production and transportation systems of gaseous raw hydrocarbons, the techniques development for gas-hydrate-deposits potential estimation and production variants calculation. The presented review shows that the most studies are carried out independently, in previously formed separate groups and laboratories. However, some investigations are made in cooperation with Russian and foreign colleagues. Also, it should be noted that all publications, presented in this review, are of a high quality.

Offshore oil and gas fields are actively developed nowadays. Moreover, due to the depletion of conventional offshore reserves, fields of Arctic shelf seem to be most promising. Offshore hydrocarbon production is carried out by means of various constructions, including floating platforms. Such platforms play a special role in offshore field development and are essential for production in deepwater. In this paper functionality of several platforms are described and the advantages of some architectural and structural designs are analyzed. Particular attention is paid to various cylindrical floating platforms with low draft. Ultimately, it turned out that the BUOY type floating platform is of the greatest interest for Arctic shelf conditions. Its design allows for operation in difficult ice conditions, i. e. in the ice zones of freezing seas. The design of support blocks with various faces, that provide reduction of both ice and wave loads on the platform, as well as decreasing of pitching in swell conditions, is also analyzed in the article. The presented solution provides effective resistance against ice fields due to destroying them and redirecting the main impact vector. Thus, this design of support block of floating platform has great potential for the development of Arctic resources of offshore oil and gas fields.

Sound emission by pipelines' open sections is one of the three primary noise sources on the territories of main gas pipelines compressor stations. Sound-emitting open sections of pipelines (superchargers' process piping) are placed above ground, on the top side of compressor yards, for process reasons. As a result, the noise level reaches 90–100 dBA and more in their proximity, and up to 85–87 dBA at the compressor stations' territories, which entails adverse working conditions for maintenance staff [1]. Gazprom VNIIGAZ LLC has developed an algorithm for gas transportation noise protection. It involves three possible activities to reduce the noise level of pipelines' open sections [1]: using low-noise natural gas superchargers with the simultaneous elaboration of smooth piping turns, installation of in-pipe noise killers, or soundproofing pipeline surfaces. Unfortunately, low-noise superchargers are only theoretically possible at the present level of technology, and the smooth piping turns require large areas and increase the structures' metal consumption. In-pipe noise killers are more technically feasible and very effective, though they have not been used until recently due to process issues. On the other hand, the acoustic coating of pipeline surfaces is widely used. The article gives the results of the extensive bench and full-scale testing of different types of soundproofing structures. Different test benches were used, including those within RAACS and full-scale testing at actually operating plants. As a result, some recommendations were developed for the effective use of soundproofing structures. It is found that elastomer-based structures have a significant advantage in soundproofing pipelines. The study shows the results of using an elastomer-based soundproofing structure at an operating compressor station. In addition to the acoustic structure on the open pipeline surface, detachably-mounted enclosures were installed for the first time on the block and control valves of superchargers' process piping. The plant noise level met the sanitary regulations after the implementation of this activity. After the necessary customization, this technique can be successfully used in other business segments of PJSC Gazprom, where there are cylindrical or flat surfaces with highly-intensive sound emission: in natural gas production, transportation, and processing.

The paper sets out the objectives of studying pipe materials, designs, and protective coatings with regard to operating conditions of deep-water gas pipelines. It also gives a classification for events and failures in the form of local ruptures or depressurization of these engineering structures. The subject's research experience is shown for the Black Sea conditions. The selection of electric-welded pipes is justified by analyzing their operability under water and gas pressure and bending. It is noted that pipes shall have minimum deviations from standard thicknesses and straightnesses. An integrated pipe examination program is presented that includes standard mechanical and chemical examinations, special bearing and bending (buckling and lateral bending) tests of pipe sections, and full-scale experiments at different depths in the Black Sea. The article also provides the research results for materials' corrosion resistance and protective coating effectiveness under the corrosive medium and high pressures. It also analyzes the full-scale offshore tests' results for pipes and their sacrificial protection and proposes steel grades and materials for sacrifice anodes. The integrated examination has made it possible to develop recommendations for selecting the best materials and designs for deep-water gas pipeline construction projects in the Black Sea and other prospective regions.

The article aims to reveal the new efficient approach to planning energy resources consumed by PJSC Gazprom's gas transportation subsidiaries for natural gas compression and chilling. These resources constitute at least 97 % of the total expense for gas transportation, making this paper quite relevant. It describes a physical law for calculating the natural gas consumption for gas flow energy recovery in a gas pumping unit. The article's novelty lies in the justification of revising resource consumption planning for gas transportation based on a cubic function with a confidence interval. The study argues that it is unfeasible to determine detailed consumption in advance because of the scatter in daily energy resource consumption influenced by various factors. An alternative approach is proposed to correct the existing procedure: calculating the amount of resource needed based on commodity transportation and multiplying it by the gas transportation system's load factor. The article also summarizes pilot tests performed at Gazprom transgaz Yugorsk LLC and Gazprom transgaz Nizhny Novgorod LLC. The results show some ways to reduce the energy resource consumption for gas transportation, which proved to be the most efficient. We also stress the necessity of achieving an integrated economic effect from implementing new resource management technologies for gas transportation, which would improve the PJSC Gazprom's energy-saving program. The rationale is set for the efficiency of automation technologies that would plan the energy resource consumption using mathematical simulation.