Welcome to ROS
The ROS Theses Repository contains full-text copies of all Heriot-Watt University PhD theses awarded from 2009 onwards.
It is mandatory for any student who completes a doctoral thesis to submit a digital copy for inclusion in ROS. In addition, the metadata-only records of older theses (previously held in the University Library catalogue) are included in ROS, with full text digital copies being sought on a voluntary basis. If you have a digital copy of your thesis and you wish to store it in ROS, please contact us.
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Recent Submissions
Spectral clustering of directed and time-evolving graphs : theory and applications
(Mathematical and Computer Sciences, 2025-08) Trower, Maia; Klus, Associate Professor Stefan
Asphaltene deposition : an experimental study using Quartz Crystal Microbalance technology
(Heriot-Watt University, 2025-05) Ghaffoori, Abeer Tareq; Burgass, Doctor Rhoderick William; Chapoy, Professor Antonin; Ahmadi, Pezhman
Asphaltene deposition is a significant flow assurance challenge in oil production. Any factor
interrupting the thermodynamic equilibrium that keeps asphaltenes miscible with the liquid
phase can result in precipitation, accumulation, and potential deposition. This may deposit in the
formation, wellbore, or production lines, causing reduced flow or complete blockage. Chemical
inhibitors are mainly used to mitigate asphaltene deposition risk in the field. The type of oil and
the production conditions dictate the use of various chemistries, making laboratory-based test
methods for asphaltene inhibitor screening crucial for recommending the best chemical solution.
Recent interest in the industry has shifted towards the use of a real-time deposition-based sensor
called Quartz Crystal Microbalance (QCM) for problematic crude oils, especially with low
asphaltene content (< 1%). Testing such crude oils using more traditional techniques is often
difficult because they produce a very small gravimetrically measurable deposit. Often, only a
limited amount of crude oil is available for laboratory testing, exacerbating this challenge. This is
where the nano-gram detection resolution of QCM can be beneficial.
QCM testing is susceptible and very sensitive to the test conditions used, as the vibration
frequency of the quartz crystal is impacted by a multitude of factors, including pressure and
temperature, viscosity, localized gas bubble formation, and film buildup/adhesion of non-analyte
materials onto the crystal surface.
As future oil production moves to more problematic and challenging reservoir and production
conditions, it is necessary to look beyond conventional methods for improved lab-to-field
correlation. Therefore, this thesis aims to develop procedure of an experimental st-up that can
measure all phase changes in live crude oils across a broad range of pressure and temperature in
a single test. That helps evaluate/develop chemical inhibitors in more realistic conditions with
optimum time. If you design the control system and test program appropriately, QCM testing can
provide useful information.
Results demonstrate the high pressure/high temperature (HPHT~) QCM to be a very promising
tool for asphaltene inhibitor evaluation, with clear variations in anti-deposition performance seen for different chemicals. The HPHT QCM studies presented here can address the challenge
of accurately measuring chemical effectiveness in problematic crude oils containing low
asphaltene content. Accordingly, an interesting trend was noted in shifting frequency trend at
asphaltene onset pressure (AOP) and relative asphaltene mass deposition on QCM with different
chemical treatments under high pressure and temperature conditions relevant to field
conditions. In addition to mass build-up, the shift in AOP can be another useful key performance
indicator (KPI) for chemical effectiveness, which needs further understanding. In this work,
evaluating the oil sample under various simulated realistic production scenario aids in
comprehending the test's limitations and consolidating the optimal program design for HPHT
QCM.
Also, results from atmospheric pressure dead oil titration tests often match up well with results
from re-liven HPHT tests. However, there are big differences for some inhibitors, which means
that the results from atmospheric pressure dead oil titration tests may not always reflect real
conditions. The chemical performance from re-livened HPHT tests were significantly influenced
by diverse setting conditions, promoting the design of practical inhibitors tailored to address each
proposed case.
Overall, these observed differences may go some way to explain problematic discrepancies
between traditional results using laboratory test methods results and real-field chemical
treatment performance, i.e., where an inhibitor performs well in the laboratory, but not in the
field.
Towards an integrated digital transformation framework for Industry 5.0 : enablers, barriers, and the ambidexterity solution
(Heriot-Watt University, 2025-06) Mohankumar, Sandeep; Tran, Doctor Yen
Digital transformation (DT) is crucial for organizations to thrive in the digital era, driven
by Industry 4.0 and further accelerated by Industry 5.0. However, unsuccessful DT
initiatives can be detrimental to organisational performance, highlighting the need for
pragmatic DT strategies aligned with operational goals and sustainable value creation. A
comprehensive DT strategy must encompass organisational, technological, and human
dimensions. Furthermore, organizations must simultaneously exploit their existing
business models while exploring new digital opportunities - a capability known as
organisational ambidexterity - to ensure sustained growth and competitiveness in an ever-evolving market landscape.
Despite its significance, existing studies on DT lack an integrated perspective on the
enabling and deterring factors that influence the success of DT initiatives. Additionally,
there is a notable absence of a comprehensive framework to support organizations in
effectively strategizing and implementing DT while maintaining organisational
ambidexterity. This research addresses these significant gaps by systematically
investigating the enablers and deterrents of DT and developing a comprehensive,
actionable DT framework. The proposed framework equips organizations with a
structured approach to achieving their DT objectives while successfully practicing
ambidexterity.
This study adopted an inductive approach combined with an explanatory sequential
design to investigate how organizations navigate the complexities of DT while balancing
tradition and innovation. The research began with an extensive literature review to
identify and analyse the key constituents and frameworks of DT, emphasizing critical
success factors and the application of organisational ambidexterity within the context of
DT initiatives. Insights derived from this review were further explored through
quantitative surveys and qualitative semi-structured interviews conducted with a
carefully selected sample of organizations in Oman.
This research makes a significant theoretical contribution to knowledge by offering an
integrated perspective on the critical factors influencing DT and enhancing the
understanding of organisational ambidexterity within the context of DT. From a practical
standpoint, the study presents a comprehensive DT Framework, grounded in theoretical
insights and pragmatically designed, offering organizations a structured approach to
strategizing and implementing DT initiatives. Furthermore, this research proposes an
'ambidexterity solution' to balance exploitation and exploration in effectively practicing
digital transformation.
Pore-scale modeling of ganglion dynamics
(Heriot-Watt University, 2025-05) Amani, Mohammad; van Dijke, Doctor Rink
In this study, a dynamic pore [bodies] and throats model was developed to analyze ganglion
dynamics within porous media, transitioning from a bond model to a novel pores and throats
framework. Building upon the limitations identified in the bond model and insights gained from
direct numerical simulations at TotalEnergies GRC, this new model incorporates innovative
techniques for tracking disconnected oil clusters, integrating capillary pressure, fluid
distribution at pore intersections, and defining time steps. These enhancements facilitate a more
accurate simulation of ganglion dynamics, including break-up and coalescence events, which
are essential for understanding multiphase flow.
An overview is provided presenting the limitations of the only existing pore network model that
contains [limited] ganglion dynamics, as detailed in Boujelben’s thesis (Boujelben, 2017). The
discussion highlights the inadequacy of bond models in capturing the complexities of ganglion
dynamics due to their oversimplified fluid distribution mechanisms at pore intersections and the
competition between frontal and wetting layer displacements as well as between viscous and
capillary forces.
Direct numerical studies using a Lattice-Boltzmann based simulator at TotalEnergies GRC
revealed critical insights into the roles of cohesion and adhesion in fluid distribution at pore
junctions. These findings prompted the development of a new pores and throats model, moving
away from the phase flag approach to a saturation-based evaluation of multiphase
displacements.
The new model, detailed in Chapter 5, incorporates novel capillary pressure inclusion based on
the content of adjacent pore elements and uses findings from direct numerical simulations to
simulate fluid distribution accurately. The model also introduces a novel time-step definition
and allows for multiphase injection and flow within each pore element, enhancing the
simulation's realism. The model was validated against micromodel experiments and
demonstrated independence from network generation, dimensions, and size. The model's
efficiency improvements are then illustrated as well as its application in analyzing the effects
of various parameters on multiphase displacements. The critical role of ganglion dynamics,
including break-up, coalescence, stranding, and mobilization events, in determining the degree
of oil displacement by water is highlighted. This research significantly advances the understanding of multiphase flow at the pore-scale,
offering a robust framework for future studies and practical applications in enhanced oil
recovery and other subsurface fluid dynamics fields.
The role of passive continental margin rugosity on Alpine thrust system geometry in the Central Mediterranean
(Heriot-Watt University, 2019-06) Polymeni, Anastasia; Underhill, Professor John R.; Jamieson, Doctor Rachel M.; Gerdes, Professor Keith
Currently unavaiable theses restricted.