Doctoral Theses (Energy, Geoscience, Infrastructure and Society)
Permanent URI for this collectionhttps://hdl.handle.net/10399/2794
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Item 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 KeithCurrently unavaiable theses restricted.Item Experimental investigation of the thermophysical properties affecting CO₂ enhanced oil recovery(Heriot-Watt University, 2025-08) Alor, Emmanuel; Chapoy, Professor Antonin; Burgass, Doctor RodUnderstanding fluid properties in relation to pressure and temperature is crucial for reservoir engineers as they evaluate production performance and manage reservoirs for enhanced crude oil recovery. Additionally, in the context of global decarbonization goals, carbon capture, utilization, and storage (CCUS) have emerged as pertinent strategies. Among these, CO2- enhanced oil recovery (CO2-EOR) stands out due to its intrinsic storage of CO2 in geological formations, making it an attractive option given the challenges and costs associated with finding new reservoirs. CO2-EOR involves five key mechanisms: (1) oil volume swelling, (2) reduction in oil and water density, (3) reduction in oil viscosity, (4) reduction in interfacial tension, and (5) vaporization and extraction of portions of oil, particularly the lighter components. Carbon dioxide exhibits high solubility in hydrocarbons, leading to oil swelling and consequent reductions in viscosity and density. As a result, comprehending the impact of pressure, volume, and temperature (PVT) on the behavior of carbon dioxide and hydrocarbon mixtures becomes imperative in this context. This study focuses on examining the impact of CO2 presence in hydrocarbons through an investigation into the thermophysical properties of binary mixtures comprising CO2 and hydrocarbons. Bubble point measurement was carried at mole fraction CO2 of approximately 0.75 and 0.35, and temperature range of 320 to 400 K. The bubble point of the mixtures were measured with a setup which consists of an equilibrium cell, cryostat, rocking/pivot mechanism, and temperature/pressure recording equipment controlled by a PC. The equilibrium cell is a piston-type variable volume (maximum effective volume of 300 ml), titanium cylindrical pressure vessel with mixing ball, mounted on a horizontal pivot with associated stand for pneumatic controlled rocking through 180 degrees. Cell volume, hence, pressure, can be adjusted by injecting/withdrawal of liquid behind the moving piston. The cell was charged with the test sample and set to the desired temperature for the measurement. The sample volume was then reduced by pumping liquid into the cell (behind the moving piston), at the opposite end to the sample. By this means the sample pressure was increased such that the sample was at a pressure significantly higher than the expected bubble point pressure. The cell was then rocked to mix the contents and ensure equilibrium. The sample temperature was then decreased step-wise until the fluid moves from 1-phase region to a 2-phase region. The stabilized equilibrium pressures and temperature were plotted and the bubble point was indicated by a sharp change in the pressure versus temperature plot. The findings reveal that an elevation in pressure leads to a reduction in viscosity at a constant temperature. Similarly, an increase in temperature results in a decrease in viscosity and density at constant pressure. The interfacial tension (IFT) between CO2 and hydrocarbons follows an almost linear decrease with rising pressure and an increase with temperature. Additionally, the bubble point experiences an increase with a rise in temperature at a constant mole fraction. Furthermore, an increase in the mole fraction of CO2 corresponds to an increased bubble point at a constant temperature. Notably, at a constant CO2 fraction, mixtures with higher carbon numbers exhibit higher boiling points. Bubble points using Peng Robinson equation of state were calculated and compared to our measurements at the same temperature, pressure and mole fraction xCO2, It gave a good correlation. Also, the model that showed the best match with literature data for IFT is the density gradient theory (DGT). GERG 2008 and Peng Robinson performed very well for most of the density predictions.Item Stratigraphic and sedimentary evolution of the Guyana Basin : implications for slope stability and geohazards(Heriot-Watt University, 2025-08) Saul, Deron; Nicholson, Doctor UisdeanAbstract and full text unavailable. Restricted access until 14.03.2028. Please refer to PDF.Item Plankton composition and dynamics in coastal waters around Gibraltar(Heriot-Watt University, 2025-08) Stagnetto, Lewis Sebastian; Poulton, Professor AlexEnvironmental conditions are key in driving biological changes within any given community. Phytoplankton communities are no different. Therefore, understanding the physical parameters which are driving oceanic chemistry within the Straits of Gibraltar and coastal waters of Gibraltar is fundamental in understanding the changes being observed in the biological communities. Although much work has been done to try and unravel the drivers of physical and chemical changes, further work is required to better understand exactly how these changes manifest themselves in an unpredictable stretch of water like the Straits of Gibraltar. This thesis reviews much of the work that has been accumulating over the last quinquagenary and attempts to collate and discern potential implications of these findings within the Straits of Gibraltar. To establish a broad scale baseline for the coastal waters around Gibraltar a 24-year satellite data series was compiled to establish climatology’s on sea surface temperature, chlorophyll, photosynthetically active radiation, and the attenuation co-efficient of photosynthetically active radiation to create a larger scale understanding of environmental trends. This work is important to contextualise the in situ data which has been collected. The in situ data allows more fine analysis in the southern British Gibraltar territorial waters and adds a depth component to it. This is important for understanding how the water column changes seasonally and for measuring how large these changes are. By obtaining fluorescence measurements from chlorophyll and phycoerythrin it was possible to establish a relationship between the two. The ratio of the two pigments was compared with others obtained in the literature and then a physiologically based ratio was applied to estimate the contribution of cyanobacteria chlorophyll to the total community chlorophyll and investigate community composition. Predation in the form of grazing, is an important top-down pressure in marine ecosystems which controls community composition. This pressure can be selective on a small number of species or it can be broad, which affects the whole community. But who grazes the grazers and what are the possible trophic effects within an ecosystem? In order to explore this question, the predation of grazers is considered by investigating how jellyfish can alter a population of grazers of zooplankton.Item Activity of governance with the purpose of sustainable development : evaluating the role of local stadiums in cities’ green governance transition(Heriot-Watt University, 2025-08) Toloue Hayat Azar, Parisa; Smith, Professor Harry; Walker, Professor GuyPresent-day governance consists of collaboration between diverse system elements for the purpose of achieving desired outcomes. For decades, cities have sought to reduce GHG emissions, particularly the ones deriving from transport. However, stadiums, which are ubiquitous in cities, remain overlooked within the realm of urban sustainability governance. This thesis examines how stadiums might be integrated into city governance to support the transition toward sustainable development. This thesis adopts Cognitive Work Analysis as a framework for examining complex socio-technical systems by first constructing a domain model. The framework then moves towards optimisation of the system performance: Strategies Analysis checks that all necessary tasks for the domain’s operation are in place. The Social Organisation and Cooperation assesses whether the teams responsible are competent and how effectively they collaborate towards achieving the system’s goals. Therefore, this thesis is comprised of a theoretical section which, through carefully analysing various philosophies based on historical descriptions, develops a domain model of governance for sustainable development and explores the potential roles of stadiums within it; and an empirical one focused on Edinburgh’s green transport governance. The theoretical section informed both the data analysis and the design of the surveys presented in the empirical section. Potential strategic problems were identified through published documents, talks, interviews, as well as user observations and surveys. Bottom-up and top-down views on stadium involvement as a solution were assessed through surveys, a case study, and interviews. These analyses lead to the conclusion that assigning constructive social roles to stadiums are often overlooked in policymaking, and that the same hold untapped potential in strengthening contemporary governance by effectively addressing the challenge of citizen engagement.Item Insights into algal nutrient uptake and carbon dynamics(Heriot-Watt University, 2025-07) McMinn, William Robert; Poulton, Professor Alex; Periera, Doctor RyanMarine phytoplankton are a pivotal component of the global carbon cycle and are routinely modelled in Earth System Models as it is believed that their physiology is well understood. The key studies for nutrient uptake occurred in the period 1967 to 1985, and the subject has received little attention since. Re-examining nutrient uptake at sub-hourly scales using Lab-On-Chip (LoC) sensors was the original plan for this study, but technical issues made this impossible, and so experimental cultures were grown with daily samples taken. A compilation of all published data on algal nutrient uptake was undertaken and examined in the context of variability in cell size, taxonomy, nutrient resource and whether active or passive nutrient uptake prevails. Despite published linear relationships between cell size and nutrient uptake, this could not be found in the data compilation leading to an impression that algal nutrient uptake is not an active process supported by transmembrane transporters. The new database also revealed significant commonality in nutrient uptake kinetics between different taxa and for different nutrient sources, so that competition between microalgae is not governed by nutrients and other processes must be important for species and taxonomic succession. Dissolved Organic Carbon (DOC) is an important component of the marine carbon cycle, with Dissolved Organic Matter (DOM) including a mixture of DIC, Dissolved Organic Nitrogen (DON) and Dissolved Organic Phosphorus. Experiments to couple nutrient uptake and measurements of DOC and DON release were undertaken in parallel. Rapid (<1 day) and short-term (2-4 days) changes in the DOM composition were detected in the cultures, when growth rates were low and increases in cell density were not established. The mechanisms behind these short-term changes, whether induced by exposure to light or microbial activity in the cultures, is unclear but warrants future focus. A notable difficulty in the work was that the aged seawater used as a media base contained a significant DOC and DOM signal that overrode the potential magnitude of release by phytoplankton.Item Deep learning for well-to-seismic data mapping and reconstruction(Heriot-Watt University, 2025-07) Abd Rahman, Ahmad Sharif; Elsheikh, Professor AhmedSeismic inversion, a critical geophysical technique for quantitative subsurface characterization, faces persistent challenges including the scarcity of labeled well-log data, the non-stationarity of seismic signals, the ill-posedness of multi-parameter estimation from limited-offset data, and practical difficulties with real-field data imperfections. This thesis introduces innovative deep semi-supervised learning (DSSL) frameworks to enhance inversion accuracy, robustness, and data efficiency. The methodology employs 1-D U-Net architectures in DSSL paradigms, learning from limited labeled and abundant unlabeled seismic data. It integrates physical principles via neural network emulators of complex wave phenomena and explicit non-stationary forward models. Specialized training, including two-phase/stage learning, on-the-fly synthetic data generation, consistency regularization, Total Variation loss, and adaptive masking, are employed to optimize performance and generalization. This research demonstrates DSSL’s efficacy across key inversion problems: first, for reflectivity inversion, effectively handling sparsity and non-stationary wavelets with limited data; second, for simultaneous acoustic impedance and density estimation from zero-offset data using a physics-based reconstructor, achieving accuracy even with extreme data scarcity; third, by explicitly modeling wavelet non-stationarity for improved accuracy and spectral fidelity; and finally, by robustly tackling real-field geometric well-seismic misalignments and incomplete logs through novel alignment and masking. The proposed DSSL frameworks consistently surpass traditional and supervised learning benchmarks, offering superior accuracy, enhanced geological plausibility, and notable computational efficiency. This thesis delivers novel, practical, data-efficient solutions to enduring seismic inversion challenges by intelligently integrating deep learning with geophysical domain knowledge. The developed techniques hold significant potential for improving subsurface exploration, characterization, and management in diverse energy and environmental applications.Item Economic feasibility of carbon storage for further use in enhanced hydrocarbon recovery(Heriot-Watt University, 2025-07) Kadafur, Ibrahim Bulama; Jafarizadeh, Doctor Babak; Mackey, Professor EricCarbon Capture, Utilisation, and Storage (CCUS) projects face significant economic feasibility challenges, often influenced by fluctuations in carbon allowance prices and the financial credits associated with removing atmospheric carbon. Another factor contributing to setbacks in the technology is the uncertainty surrounding carbon’s future path. While most studies have concentrated on the technical aspects of CCUS, this research shifts focus toward economic evaluations, specifically investigating the feasibility and potential for value creation through storing CO₂ in a saline aquifer as a buffer to recycling CO2 being used for EOR in a neighbouring hydrocarbon field. This interdisciplinary work offers information on CCUS technology and insights into the relationship between CCUS and project valuation economics. The core aim of the research is to address both technical and economic perspectives, avoiding the overly technical or overly financial reports and publications typically found in the literature. The significance of this research lies in its potential to inform and contribute to academic, industry, and policy discussions on CCUS economics and technology, thereby advancing the field of sustainable energy. The study models the economic value of such projects by analysing carbon allowance prices in commodity markets. It uses a two-factor stochastic model to forecast future spot prices, applying the framework from referenced sources and the Sum-of-Discounted-Prices technique. This generates low, expected, and high carbon price forecasts for economic evaluation. The research simulates hydrocarbon production and optimisation in the Pembina Cardium field, focusing on water and CO2 injection rates and cycles. It also assesses whether buffer storage offers economic benefits over sourcing CO2 externally, examines CO2 recoverability, and identifies optimal well architecture, production strategies, and injection constraints. Furthermore, the study employed an integrated techno-economic model to evaluate decision options, incorporating commodity prices, simulation results, penalties, taxes, royalties, discount rates, and other relevant factors, thereby facilitating a transparent analysis and valuation of investments. It also incorporated decision tree analysis and Monte Carlo Simulation for better decision-making. Finally, the research demonstrates that deploying vertical wells in layered formations or reservoirs with low vertical permeability for carbon buffer storage in saline aquifers yields higher carbon recovery and minimises associated water production. The valuation analyses reveal that integrating buffer carbon storage substantially boosts hydrocarbon production from depleting reservoirs and improves overall project valuation regardless of the prevailing carbon emission regulatory regime. This dual benefit not only facilitates effective CO₂ sequestration but also contributes to more efficient and sustainable production processes. As a result, it addresses key dimensions of the energy trilemma by lowering production costs, enhancing hydrocarbon recovery, and reducing carbon emissions, providing practical insights for sustainable energy development.Item On the phase behaviour of CCS fluid systems(Heriot-Watt University, 2025-07) Okoro, Franklin; Chapoy, Professor Antonin; Burgass, Doctor Rod; Ahmadi, Doctor PezhmanThis study investigated the phase behaviour of CO₂-rich mixtures containing co-capture impurities at low temperatures, which is critical for carbon capture, utilisation, and storage (CCUS) applications, particularly in offshore CO₂ transport by ship at temperatures as low as 223.15 K. Due to limited data on CO₂-rich systems at these conditions, the study conducted constant composition expansion and isochoric experiments to assess the effects of impurities - such as Methane (CH4), Oxygen (O2), Argon (Ar), Nitrogen (N2), Hydrogen (H2), Carbon monoxide (CO), and Dimethyl ether (DME) on the phase behaviour of CO2-streams at low temperatures. Temperature and pressure measurement uncertainties were 0.14 K and 0.03 MPa, respectively. The study findings show that non-condensable impurities generally raise bubble point and dew point pressures, with hydrogen having the most significant impact due to its high volatility, followed by nitrogen. In contrast, the relatively low volatility of DME results in negative deviations of the CO₂ stream from pure CO₂ phase behaviour. Model validation revealed that the Peng–Robinson equation of state (EoS), with adjusted binary interaction parameters (BIPs), provided the most accurate predictions, with average absolute deviations (AAD) below 5% for all datasets. The study also collected new bubble and dew point data for seven CO₂-rich multicomponent systems across temperatures from 238.15 K to near their critical points. Even at low impurity levels, bubble point pressures increased significantly at lower temperatures, while dew point pressure effects only became substantial at higher impurity concentrations. Both the Peng-Robinson and MFHEA EoS models predicted the data well, with AADs below 3.4% for dew and bubble points. These insights are essential for optimising CCUS transport and storage, as impurity effects necessitate careful temperature and pressure management to ensure safe and efficient CO₂ handling in pipelines and storage vessels.Item Using outrigger systems from steel plates in tall reinforced concrete buildings(Heriot-Watt University, 2025-06) Habrah, Alaa Adnan; Batikha, Doctor Mustafa; Vasdravellis, Doctor GeorgeAs the population grows and available land becomes more limited, high-rise buildings have become a popular and sustainable solution to maintain agricultural areas. The evolution of tall building design has been marked by the rise of innovative structural lateral resisting systems. Among these, the core-outrigger system has emerged as a highly efficient solution for mitigating drift and core overturning moments in tall buildings. Studies have suggested various types of outrigger infills, including steel bracing, reinforced concrete, buckling-restrained bracing, and more.. Very few studies have proposed using steel plates as an outrigger infill. This research offers a new outrigger system, the Steel Plate-infilled Reinforced Concrete Frame (SP-RCF), to enhance high-rise building performance by taking advantage of the state-of-the-art properties of thin steel plates and integrating them into reinforced concrete boundary frames. To ensure the new system’s effectiveness, a theoretical foundation was established by analytically determining the optimal number and placement of outriggers and providing practical graphs to be used in the initial design stage for any outrigger type. This was followed by nonlinear simulations in ABAQUS, where a full-scale SP-RCF’s behavior in terms of stiffness, strength and ductility was assessed against the most common outriggers, namely Reinforced Concrete Wall-infilled Reinforced Concrete Frame (RCW-RCF) and Steel Truss-infilled Reinforced Concrete Frame (ST-RCF). Finally, the three outriggers were integrated into a full-scale high-rise case study using ETABS software to simulate and compare their impact on global building behavior under severe seismic loading through static nonlinear analysis. The outcomes of this study demonstrated that the SP-RCF system, compared to conventional outriggers, achieved notable structural enhancements of up to 75% in strength, 18% in post-yield stiffness, 43% overstrength capacity, and 29% in the response modification factor. The findings are evidence of the advantages the proposed system in this study will add if implemented.