Multiphase flow instability and active slug control solutions
| dc.contributor.advisor | Cao, Yi | |
| dc.contributor.author | Tandoh, Henry Kwaw Ayisi | |
| dc.date.accessioned | 2022-06-15T10:49:30Z | |
| dc.date.available | 2022-06-15T10:49:30Z | |
| dc.date.issued | 2018-03 | |
| dc.description.abstract | Slugging as a flow assurance challenge is an upsetting condition to the oil and gas industry due to the instabilities it poses on the system. The negative repercussions associated with slug flow stems from the inlet through to the topside facilities where processing is done. Active control has been established as one of the best techniques to eradicate slug and its accompanying challenges however the controller robustness and some setbacks make improvement a necessity. In that vein, the Inferential slug controller which uses a combination of topside measurement signals to produce a single control variable which is more sensitive to slug variations hence can effectively be used to control slug, was invented. Again the robustness of this controller has been in question. This study presents a comprehensive and systematic analysis of the Inferential slug controller design for system stability analysis and maximising throughput from unstable riser pipeline system configurations in the quest to advance this technology. The inferential slug controller’s robustness was assessed by implementing this technique on several pipeline riser systems including U-shape and S-shape riser configurations. Prior to that, the flow behaviour for a wide range of flow conditions was investigated, highlighting the impact of geometry on unstable slug flow through the OLGA flow simulator (modelling) and experiments. New and unused measurement signals from the topside of either the riser/platforms were deployed in the inferential slug control technology to make the controller more sensitive and robust. A simplistic nevertheless robust procedure for designing the inferential slug controller was proposed. Unstable slug flow conditions were observed to stabilise at a relatively larger valve opening compared with that seen in open loop. The inferential slug controller technology is further extended to deal with systems with variable time delay using a proposed modified Smith predictor model. The modified Smith predictor was recorded to improve and stabilise a pipeline riser system which has deteriorated in control performance due to time delay in the system, a resultant of large stroke time in the valve. This in practicality means an increased production through the system. In advancing the ISC technology to be deployed on offshore fields in conjunction with other passive slug mitigation techniques, the slug mitigation potential of pseudo spiral tube (PST) was assessed when installed at the topside of the riser system. The analysis showed that the PST pipe section (spiral and wavy piece) when installed at the topside of the riser system, possesses some mitigation potential. Four different slug regions was identified for the entire pipeline system. The first region being a slug flow occurrence in the system with and without the PST whiles the second region is the region where slugging occurs in the system but disappears when coupled with the PST and the opposite describes the third region. Lastly, the fourth region is described as that region where slugging flow exist for the system coupled with the spiral pipe section and without any PST (plain) but slugging flow disappears when the system is coupled with the wavy pipe section. The wavy or spiral pipe section coupled with the S-shape riser system have slug mitigation capabilities when they are installed at the top of the riser although its effectiveness of slug mitigation depends on the flow condition. This is evident in the significant reduction in the riserbase pressure oscillation magnitude and the significant reduction in the slug envelope (region) when the system was coupled with the wavy or spiral pipe section relative to the plain system. | en_UK |
| dc.description.coursename | PhD in Energy and Power | en_UK |
| dc.identifier.uri | http://dspace.lib.cranfield.ac.uk/handle/1826/18027 | |
| dc.language.iso | en | en_UK |
| dc.rights | © Cranfield University, 2015. All rights reserved. No part of this publication may be reproduced without the written permission of the copyright holder. | |
| dc.subject | Slugging | en_UK |
| dc.subject | active control | en_UK |
| dc.subject | inferential slug contoller | en_UK |
| dc.subject | pseudo spiral tube | en_UK |
| dc.subject | Smith predictor | en_UK |
| dc.title | Multiphase flow instability and active slug control solutions | en_UK |
| dc.type | Thesis | en_UK |