TY - JOUR

T1 - Texture, composition and properties of plugs formed by carbon dioxide hydrate and wax

AU - SKIBA, Sergey

AU - SAGIDULLIN, Aleksey

AU - SHAPOVALOVA, Alexandra

AU - STRELETS, Larisa

AU - MANAKOV, Andrey

N1 - Funding Information: The preparation of the plugs, the X-ray diffraction experiment, and the infrared spectroscopy experiment were supported by the Russian Science Foundation (17-17-01085). All other experiments were carried out within the frame-work of the Basic Research Programs of the Nikolaev Institute of Inorganic Chemistry SB RAS and the Institute of Petroleum Chemistry SB RAS. Publisher Copyright: © 2021 Research Institute of Petroleum Exploration & Development, PetroChina

PY - 2021/12

Y1 - 2021/12

N2 - Gas hydrates and wax are the major flow assurance problems for the transportation of produced hydrocarbons through pipelines. However, in most research works both these two problems are studied separately. Although simultaneous precipitation or deposition of these compounds in pipelines can lead to different mitigation/prevention strategies, the investigations in which both these problems are considered simultaneously appeared only recently. There is no information in the literature on the texture/composition and features of decomposition process of mixed wax/hydrate plugs. At the same time, this information could be useful to understand how to treat the problem of formation of these plugs. In this work, three wax/gas hydrate plugs were collected at quasi-static conditions from a water-in-oil emulsion to study their texture, composition and the features of decomposition process. Powder X-ray diffraction and IR (infrared spectroscopy) analyses showed that the plugs consisted of wax and gas hydrate. Thermovolumetric and DSC (Differential Scanning Calorimetry) experiments showed that the main part of gas hydrate in the plugs at the ambient pressure started to decompose at about 268 K. This temperature was higher than the equilibrium temperature of carbon dioxide hydrate at this pressure, indicating that the gas hydrate in the plugs could be effectively preserved at temperatures below the ice melting point (273.2 K). It was found through observation of the hydrate decomposition process in the plugs under the microscope that the gas in the samples released in small bubbles, while the hydrate particles were not visible at this magnification, indicating that the hydrate was indeed highly dispersed in the samples. A residual wax was jelly-like after decomposition of hydrate in all the cases. Rheological experiments showed that the plugs residues after decomposition of the hydrates had higher yield points and viscosities than the initial waxy crude oil originally used for the experiments.

AB - Gas hydrates and wax are the major flow assurance problems for the transportation of produced hydrocarbons through pipelines. However, in most research works both these two problems are studied separately. Although simultaneous precipitation or deposition of these compounds in pipelines can lead to different mitigation/prevention strategies, the investigations in which both these problems are considered simultaneously appeared only recently. There is no information in the literature on the texture/composition and features of decomposition process of mixed wax/hydrate plugs. At the same time, this information could be useful to understand how to treat the problem of formation of these plugs. In this work, three wax/gas hydrate plugs were collected at quasi-static conditions from a water-in-oil emulsion to study their texture, composition and the features of decomposition process. Powder X-ray diffraction and IR (infrared spectroscopy) analyses showed that the plugs consisted of wax and gas hydrate. Thermovolumetric and DSC (Differential Scanning Calorimetry) experiments showed that the main part of gas hydrate in the plugs at the ambient pressure started to decompose at about 268 K. This temperature was higher than the equilibrium temperature of carbon dioxide hydrate at this pressure, indicating that the gas hydrate in the plugs could be effectively preserved at temperatures below the ice melting point (273.2 K). It was found through observation of the hydrate decomposition process in the plugs under the microscope that the gas in the samples released in small bubbles, while the hydrate particles were not visible at this magnification, indicating that the hydrate was indeed highly dispersed in the samples. A residual wax was jelly-like after decomposition of hydrate in all the cases. Rheological experiments showed that the plugs residues after decomposition of the hydrates had higher yield points and viscosities than the initial waxy crude oil originally used for the experiments.

KW - carbon dioxide hydrate

KW - hydrate decomposition

KW - hydrate/wax plug

KW - plug texture

UR - http://www.scopus.com/inward/record.url?scp=85121305094&partnerID=8YFLogxK

U2 - 10.1016/S1876-3804(21)60302-6

DO - 10.1016/S1876-3804(21)60302-6

M3 - Article

AN - SCOPUS:85121305094

VL - 48

SP - 1462

EP - 1470

JO - Petroleum Exploration and Development

JF - Petroleum Exploration and Development

SN - 1876-3804

IS - 6

ER -