Application of a transient deposition model for hydrate management in a subsea gas-condensate tieback

Thomas B. Charlton, Stuart Kegg, Julie E.P. Morgan, Luis E. Zerpa, Carolyn A. Koh, Eric F. May, Zachary M. Aman

Research output: Chapter in Book/Conference paperConference paper

Abstract

This study provides valuable insights into hydrate management strategies as the industry transitions away from complete hydrate avoidance, particularly for the development of deep-water reservoirs with stricter economic margins. Transient simulation tools, such as the deployed hydrate deposition model, extend our ability to estimate blockage likelihood from heuristics to quantitative predictions. The model is applied to an insulated subsea tieback to identify the optimal no-touch-time (NTT) and depressurization pressure (DPP) following an unplanned shutdown. Two water-production scenarios are considered, from the lowest expected to the highest manageable rates. A complete hydrate blockage is predicted when the NTT was extended several hours beyond the nominal value for the highest water-to-gas ratio (WGR). Complete blockages are predicted for both low and high WGRs when the flowline is only partially depressurized, however, longer cooldown times for the high WGR case (due to greater volumes of residual liquids) meant a blockage took more than twice as long to occur than for the low WGR case. Fully depressurized restarts are both difficult and time consuming, leading to hydrate volume fractions (with respect to the pipe volume) exceeding 30 vol.%. An alternative hydrate management strategy is identified for cases with high volumes of water production, in which the flowline is only partially depressurized once the nominal NTT has elapsed, utilising the increased heat capacity of residual liquids. This reduces the quantity of gas sent to flare and simplifies the restart procedure.

Original languageEnglish
Title of host publicationOffshore Technology Conference 2019, OTC 2019
Place of PublicationUSA
PublisherOffshore Technology Conference
ISBN (Electronic)9781613996416
Publication statusPublished - 9 May 2019
EventOffshore Technology Conference 2019, OTC 2019 - NRG Park, Houston, United States
Duration: 6 May 20199 May 2019
http://2019.otcnet.org/

Publication series

NameProceedings of the Annual Offshore Technology Conference
Volume2019-May
ISSN (Print)0160-3663

Conference

ConferenceOffshore Technology Conference 2019, OTC 2019
CountryUnited States
CityHouston
Period6/05/199/05/19
Internet address

Fingerprint

Gas condensates
Hydrates
Flowlines
Water
Gases
Liquids
Specific heat
Volume fraction
Pipe
Economics
Industry

Cite this

Charlton, T. B., Kegg, S., Morgan, J. E. P., Zerpa, L. E., Koh, C. A., May, E. F., & Aman, Z. M. (2019). Application of a transient deposition model for hydrate management in a subsea gas-condensate tieback. In Offshore Technology Conference 2019, OTC 2019 (Proceedings of the Annual Offshore Technology Conference; Vol. 2019-May). USA: Offshore Technology Conference.
Charlton, Thomas B. ; Kegg, Stuart ; Morgan, Julie E.P. ; Zerpa, Luis E. ; Koh, Carolyn A. ; May, Eric F. ; Aman, Zachary M. / Application of a transient deposition model for hydrate management in a subsea gas-condensate tieback. Offshore Technology Conference 2019, OTC 2019. USA : Offshore Technology Conference, 2019. (Proceedings of the Annual Offshore Technology Conference).
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abstract = "This study provides valuable insights into hydrate management strategies as the industry transitions away from complete hydrate avoidance, particularly for the development of deep-water reservoirs with stricter economic margins. Transient simulation tools, such as the deployed hydrate deposition model, extend our ability to estimate blockage likelihood from heuristics to quantitative predictions. The model is applied to an insulated subsea tieback to identify the optimal no-touch-time (NTT) and depressurization pressure (DPP) following an unplanned shutdown. Two water-production scenarios are considered, from the lowest expected to the highest manageable rates. A complete hydrate blockage is predicted when the NTT was extended several hours beyond the nominal value for the highest water-to-gas ratio (WGR). Complete blockages are predicted for both low and high WGRs when the flowline is only partially depressurized, however, longer cooldown times for the high WGR case (due to greater volumes of residual liquids) meant a blockage took more than twice as long to occur than for the low WGR case. Fully depressurized restarts are both difficult and time consuming, leading to hydrate volume fractions (with respect to the pipe volume) exceeding 30 vol.{\%}. An alternative hydrate management strategy is identified for cases with high volumes of water production, in which the flowline is only partially depressurized once the nominal NTT has elapsed, utilising the increased heat capacity of residual liquids. This reduces the quantity of gas sent to flare and simplifies the restart procedure.",
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Charlton, TB, Kegg, S, Morgan, JEP, Zerpa, LE, Koh, CA, May, EF & Aman, ZM 2019, Application of a transient deposition model for hydrate management in a subsea gas-condensate tieback. in Offshore Technology Conference 2019, OTC 2019. Proceedings of the Annual Offshore Technology Conference, vol. 2019-May, Offshore Technology Conference, USA, Offshore Technology Conference 2019, OTC 2019, Houston, United States, 6/05/19.

Application of a transient deposition model for hydrate management in a subsea gas-condensate tieback. / Charlton, Thomas B.; Kegg, Stuart; Morgan, Julie E.P.; Zerpa, Luis E.; Koh, Carolyn A.; May, Eric F.; Aman, Zachary M.

Offshore Technology Conference 2019, OTC 2019. USA : Offshore Technology Conference, 2019. (Proceedings of the Annual Offshore Technology Conference; Vol. 2019-May).

Research output: Chapter in Book/Conference paperConference paper

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M3 - Conference paper

T3 - Proceedings of the Annual Offshore Technology Conference

BT - Offshore Technology Conference 2019, OTC 2019

PB - Offshore Technology Conference

CY - USA

ER -

Charlton TB, Kegg S, Morgan JEP, Zerpa LE, Koh CA, May EF et al. Application of a transient deposition model for hydrate management in a subsea gas-condensate tieback. In Offshore Technology Conference 2019, OTC 2019. USA: Offshore Technology Conference. 2019. (Proceedings of the Annual Offshore Technology Conference).