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Retardation of oil cracking to gas and pressure induced combination reactions to account for viscous oil in deep petroleum basins: Evidence from oil and n-hexadecane pyrolysis at water pressures up to 900bar

Uguna, Clement N.; Carr, Andrew D.; Snape, Colin E.; Meredith, Will

Authors

Andrew D. Carr

COLIN SNAPE COLIN.SNAPE@NOTTINGHAM.AC.UK
Professor of Chemical Technology & Chemical Eng



Abstract

This study reports a laboratory pyrolysis experimental study on oil and n-hexadecane to rationalise the thermal stability of oil in deep petroleum reservoirs. Using a 25 ml Hastelloy pressure vessel, a 35° API North Sea oil (Oseberg) and n-hexadecane (n-C16), were pyrolysed separately under non-hydrous (20 bar), low pressure hydrous (175 bar) and high liquid water pressure (500 and 900 bar) at 350°C for 24 h. This study reports a laboratory pyrolysis experimental study on oil and n-hexadecane to rationalise the thermal stability of oil in deep petroleum reservoirs. Using a 25 ml Hastelloy pressure vessel, a 35° API North Sea oil (Oseberg) and n-hexadecane (n-C16), were pyrolysed separately under non-hydrous (20 bar), low pressure hydrous (175 bar) and high liquid water pressure (500 and 900 bar) at 350 °C for 24 h. This study shows that the initial cracking of oil and n-hexadecane to hydrocarbon gases was retarded in the presence of water (175 bar hydrous conditions) compared to low pressures in the absence of water (non-hydrous conditions). At 900 bar water pressure, the retardation of oil and n-hexadecane cracking was more significant compared to 175 bar hydrous and 500 bar water pressure conditions. Combination reactions have been observed for the first time in pressurised water experiments during the initial stages of cracking, resulting in the increased abundance of heavier n-alkane hydrocarbons (> C20), the amount of unresolved complex material (UCM), as well as the asphaltene content of the oil. These reactions, favoured by increasing water pressure provide a new mechanism for rationalising the thermal stability of oils, and for producing heavy oils at temperatures above which biodegradation can occur. Indeed, we demonstrate that bitumen from the high pressure Gulf of Mexico basin has been formed from lighter oil components and it possesses similar characteristics to the laboratory oils generated.

Citation

Uguna, C. N., Carr, A. D., Snape, C. E., & Meredith, W. (2016). Retardation of oil cracking to gas and pressure induced combination reactions to account for viscous oil in deep petroleum basins: Evidence from oil and n-hexadecane pyrolysis at water pressures up to 900bar. Organic Geochemistry, 97, 61-73. https://doi.org/10.1016/j.orggeochem.2016.04.007

Journal Article Type Article
Acceptance Date Apr 8, 2016
Online Publication Date Apr 16, 2016
Publication Date 2016-07
Deposit Date Jun 29, 2016
Publicly Available Date Jun 29, 2016
Journal Organic Geochemistry
Print ISSN 0146-6380
Electronic ISSN 0146-6380
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 97
Pages 61-73
DOI https://doi.org/10.1016/j.orggeochem.2016.04.007
Keywords Oil Cracking, n-Hexadecane Cracking, Oil Viscosity, High Water Pressure, Pressure Retardation, Combination Reactions
Public URL http://eprints.nottingham.ac.uk/id/eprint/34464
Publisher URL http://www.sciencedirect.com/science/article/pii/S0146638016300249
Copyright Statement Copyright information regarding this work can be found at the following address: http://creativecommons.org/licenses/by-nc-nd/4.0

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Copyright Statement
Copyright information regarding this work can be found at the following address: http://creativecommons.org/licenses/by-nc-nd/4.0





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