Doctoral Theses (Energy, Geoscience, Infrastructure and Society)
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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 A risk-oriented tender evaluation method for construction projects(Heriot-Watt University, 2019-06) Ismail, Mohd Razali Bin; Sun, Professor Ming; Bowles, Doctor GraemeEvaluating tenders is an important process performed by clients to identify qualified contractors for carrying out construction projects. Since the clients rely heavily on the contractor to manage the projects, selecting the right contractor can greatly influence the delivery of the project. Evaluating tenders based on multiple criteria has been recognised as effective in identifying the most suitable tender and minimising the risks during the construction stage. In practice, a list of criteria covering the tender’s technical capability and financial performance is often used by client organisations. However, there is little research behind the selection of these criteria and the weighting being attributed to different criteria. Moreover, there remains a paucity of evidence on the quantification of these criteria. This study seeks to establish evaluation criteria and weightings for risk-oriented tender evaluation, based on an empirical investigation involving private construction clients in Malaysia. A list of significant risks is identified first through a literature review. The risks are then mapped with the tender evaluation criteria. The selection of risks and their mappings to evaluation criteria are validated through a questionnaire survey. The weighting for the final selected evaluation criteria is established through the analytic hierarchy process (AHP) group decision making (GDM) method. Finally, the study develops criteria for numerical scoring (CNS) through synthesising tender evaluation standard operating procedure (SOP) documents of private clients and literature sources. For each CNS, the numerical rating scale is defined on a 1- 5 scale to facilitate the uniformity of scores assigned when evaluating how well a tender meets the criteria. The outcome is a tender evaluation framework, including appropriate criteria, proper weights, and criteria for numerical scoring, which is programmed in MS Excel to help clients to evaluate tenders. The system will display the risk profile of each tender and provide a recommendation for selecting a successful tender. The developed framework was validated by practitioners and tested using two case studies. Information from previous tender reports was used, and the results generated by the system suggested a different tender for award consideration as compared to the previous method.Item Investigation of enhanced oil recovery by Water Alternating Gas (WAG) injection in sandstone and carbonate rocks(Heriot-Watt University, 2019-09) Alkhazmi, Bashir Ali Abdussalam; Sohrabi, Professor MehranWater-Alternating-Gas (WAG) injection is regarded as a very efficient and successful EOR technique for lowering the residual oil in a porous medium, especially from water-flooded/gas-flooded hydrocarbon reservoirs. However, as a special case of three-phase flow, WAG injection involves complex physics and mechanisms in the process of oil recovery, for which there is still an incomplete understanding. In the literature, laboratory data on WAG processes are very limited, especially for certain conditions, such as, the ultra-low oil/gas interfacial tension (IFT), weakly/non-water-wet, non-uniform wettability and different rock types. For numerical simulation, reliable three-phase relative permeability (kr) data with their hysteresis effects are crucial for optimizing the predictions of WAG injection performance in oil reservoirs. Although the current models of three-phase relative permeability (e.g. Stone I, Stone II or Baker) and its hysteresis (e.g. WAG hysteresis) are widely applied for reservoir rocks which are non-water-wet, for their good description of pore geometry and wettability, their application is limited for a water-wet system. Since these correlations, which are available in the most widely used reservoir simulators, were developed on the basis of idealizing the rock and simplifying the assumptions, none of these correlations are able to account for the behaviours of the complex mechanisms, multi-phase flow, multi-physics processes and hysteresis phenomena involved in oil recovery by WAG flooding, especially for certain reservoir fluid conditions (e.g. ultra-low gas-oil IFT) and for oil reservoirs that are characterized by weakly-water-wet and mixed-wet rocks. Thus, reliable experimental data at realistic reservoir conditions are needed to improve our understanding of the actual mechanisms, complex physics, multi-phase flow and hysteresis behaviours underlying the oil recovery by WAG injection and to develop improved models and methodologies for reliable predictions of the performance of oil reservoirs under WAG injection. In this thesis, an extensive series of WAG coreflood experiments is reported, in which several important fluid/flow/rock characteristic properties (e.g. gas/oil IFT scaling, gas viscosity, oil-gas/oil-water viscosity ratio, steady and unsteady displacements, cyclic hysteresis, rock wettability, rock type, and remaining oil and gas saturations) and operation parameters (slug size, injection order and injection strategy) have been systematically investigated. The results of these experimental investigations are discussed in detail in terms of oil recovery, injectivity (or differential pressure) and average saturation profile (or saturation trajectories). Because the coreflood experiments were carried out on Clashach sandstone and Indiana limestone core samples the content of this thesis can be divided into two parts as follows: The first part presents the results of the investigation of the above-mentioned WAG parameters in sandstone rock with two different wettability systems (mixed-wet and weakly-water-wet). Investigating the effect of design/operation parameters on the performance of WAG flood under immiscible displacement (gas-oil IFT = 2.7 mN.m-1 ) revealed a better efficiency and higher recovery performance for short water and gas slugs compared to the large cycle injections. Comparison with the SWAG flood shows that SWAG is the upper limit of oil recovery by small slug water and gas injections. WAG injection efficiency was investigated at intermediate-miscible displacement (gas/oil IFT = 0.15 mN.m-1 ) and under mixed-wet conditions. The results are compared to those published at near-miscible and immiscible displacements to investigate the impact of IFT on the performance of WAG injection. The results showed that WAG injection performance increases as gas/oil IFT decreases and becomes optimum when approaching the critical pressure. The effect of actual rock wettability on the performance of WAG injection at near-miscible conditions (gas/oil IFT = 0.04 mN.m-1 ) is investigated for a weakly-water system, and then compared to mixed-wet and water-wet regimes. The comparison reveals that, regardless of the type of wettability, the performance of oil recovery by near-miscible WAG is considerably superior. Even though oil recovery efficiency by water flood increases as the direction of wettability changes from water-wet towards mixed-wet, passing through a weakly-water-wet stage, its performance by WAG injection, post waterflooding, decreased for the same direction of wettability changes. Two WAG experiments with two different binary-hydrocarbon fluid systems (C1-nC4 and C1-nC10) were performed under near-miscible and weakly water-wet conditions to investigate the impact of gas viscosity on gas and WAG injections. It was found that the cyclic oil recovery efficiency by water slugs was higher in C1-nC4 WAG than that in C1- nC10. In contrast, for gas cycles, it was higher in C1-nC10 that in C1-nC4. Furthermore, the gap between oil recoveries increased as the number of gas cycles increased. Two-phase and three-phase SS-kr experiments were performed under near-miscible and weakly water-wet conditions. Comparing these results with those for the unsteady state indicated significant differences in the recovery mechanisms, due to the difference in the nature of the displacement experiments. This highlights that the differences in the kr values between SS and USS in the two-phase and three-phase regions are not only pertinent to the non-uniqueness problem that is known to be associated with USS- kr , but also to the nature of the differences in the displacements, flow and mechanisms involved in oil recovery by SS and USS experiments. In the second part, a systematically acquired set of experimental data in which the effect of rock type on two-phase and three-phase flow and displacements have been investigated is presented. All experiments were conducted on a 45 mD water-wet limestone core and their results were compared to those obtained from a 65 mD water-wet sandstone core with similar physical properties to those of the carbonate. These laboratory results revealed that there is an intrinsic heterogeneity (vugs) in the internal pore structure of the carbonate rock. Comparison of WAG injection results revealed that WAG injection in sandstone, with 88.5 % (IOIP %) ultimate oil recovery outperformed that in carbonate, with 71 % (IOIP %). Finally, investigation of the effects of all the above pertinent WAG parameters on the remaining oil and gas saturations revealed that the order of fluid injection, gas/oil IFT and rock type are the most effective parameters on the slope of So,rem vs. Sg,rem trend line, which is represented by α in the WAG hysteresis model.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, Honorary Professor KeithAbstract and full text unavailable please refer to PDF.Item The impact of Olympic-led urban regeneration on ethnic minority residents in London : a right to the city perspective(Heriot-Watt University, 2019-07) Islam, Farjana; Smith, Doctor Harry; Netto, Doctor GinaThe rhetoric of the Legacy 2012 regeneration is to ‘transform the heart of East London’ emphasising creation of employment for local people and modern facilities, which were anticipated to attract mega-sporting events in the future. Since industrialisation, East London has been known to contain the poorest ethnic minority population in London, the majority of whom live in diverse ethnic enclaves. In the aftermath of deindustrialisation, the residents are experiencing unemployment, poor housing, and lower levels of educational attainment while often becoming dependent on benefit payments. In addition to the Legacy Master Planning Framework (ODA1 , 2007), LLDC2 ’s publications such as ‘A Walk around the Queen Elizabeth Olympic Park’, ‘Community Engagement Policy’, ‘Equality and Inclusion Policy’ were intended to create opportunities for the locals with a view to closing the deprivation gap between the Olympic host boroughs and the rest of London. Drawing on some of the Olympic-led urban development projects in the past, the challenge is to understand the actual benefits derived from these projects, against a background of there usually being an enormous gap between rhetoric and reality in market-driven urban regeneration projects. In this context, the research aims to explore the extent to which the legacy-led regeneration efforts have supported the inclusion of ethnic minority residents in the Legacy Corporation and its surrounding area from a ‘right to the city’ perspective. The theoretical framework adopted Purcell’s (2002) ‘right to participation’ (e.g. residents’ central role in decision making processes) and ‘right to appropriation’ (e.g. access and use of urban spaces), underpinned by Lefebvre’s (1991) philosophical notion of the ‘right to the city’. The research methodology was based on qualitative methods (i.e. semi-structured interviews, photo-elicitation interviews, and the researcher’s direct and unobtrusive observations) to gather empirical evidence from two wards – Hackney Wick and Bromley-by-Bow – with a view to exploring ethnic minority communities’ ‘de facto’ rights and ‘conjoint claims’ amidst the legacy-led regeneration process. The findings provide the basis for the argument that the games-led regeneration is contributing to an unjust trade-off between ‘deprived’ pre-existing residents and ‘upper class’ gentrifiers, ignoring the real and organic need of the poor ethnic minority communities. Moreover, at the time of fieldwork (2015), the top-down and expert-led participatory mechanisms (including residents’ direct participation, representative participation through councillors, etc.) had not ensured ethnic minority residents’ deliberate participation during planning and implementation of the regeneration projects. The empirical evidence suggests that the Olympic promise of socio-spatial transformations in terms of materialising ethnic minority residents ‘de facto’ rights and ‘conjoint claims’ (e.g. jobs, housing etc.) were sidelined to support a top-down neoliberal agenda. The research findings reveal how the targeted ethnic minority residents, although living in a pluralist society, remain socio-spatially excluded amidst the top-down legacy led regeneration process. The application of a rights-based theoretical framework increased the understanding of problems and barriers (e.g. in relation to participating and appropriating the legacy-led transformed spaces) hat hindered residents’ participation and appropriation in a top-down sport-led regeneration process. The research also contributes empirical knowledge in relation to actual benefits (e.g. jobs, housing) derived from mega-event legacies, which is important as more cities are now drawn to host mega-events with a view to achieving subsequent legacies.Item Assessment and modelling of energy use and indoor environment towards conservation in historical art gallery buildings(Heriot-Watt University, 2019-03) Ganguly, Shashwat; Wang, Doctor Fan; Chen, Doctor ZhenThis PhD study presents a set of non-invasive methods developed to assess and model the indoor environmental conditions and the building energy use in the National Galleries of Scotland (NGS). This was to meet three intentions, firstly, to provide a detailed and efficient guidance to the facility managers of such building type on the building’s indoor environmental performance with respect to artwork conservation standards, and energy performance with respect to benchmarks from official standards such as CIBSE. Secondly, to provide good practice guidance on latent energy investment towards maintaining indoor moisture conditions relative to conservation specifications. Motivation behind this moisture control was found to be the parameter which is the most critical to artwork conservation, and previous studies revealing the significant amount of energy costs associated to meet the demands of maintaining the adequate indoor moisture specifications. And thirdly, to provide a robust tool which can mimic the complex, non linear building system and provide forecasting with high speed and accuracy. This model also enables the building management to test various optimisation options, while attempting to reduce energy consumption in the building while adhering to artwork conservation standards. The assessment methods were developed following a large-scale refurbishment event in the NGS, and involved a post-renovation impact study. The latent energy investment was analysed with the help of a new weather feature variable, developed as a part of this study. This was named as ‘Humidity-Day’ (HD) concept, analogous to the Degree Day concept. Artificial Intelligence (AI) was employed to model the complex NGS building system and predict indoor temperature, RH and building energy consumption – Gas and Electricity. This directly catered to the need to test optimisation strategies to cut down energy costs without jeopardising the healthy conditions of delicate artworks housed in the building. The positive effects of refurbishment in the NGS were highlighted by performance indicators. An overall indoor environment improvement of 16% was observed, out of which maintenance of indoor RH improved by 4% and the same for temperature by 12%. Winters experienced the maximum overall indoor environmental improvement of 59%. The indoor stability assessed by newly developed fluctuation parameters for both hourly and daily cases highlighted that the NGS experienced stable indoor temperature and RH, especially after the refurbishment. In addition to the benefits to indoor environment, the refurbishment regime brought a cut-down in NGS gas consumption by 27%. The Humidity Day Concept was developed and applied as a global climatic indicator focusing on moisture extremes relative to conservation specifications. Next, the HD based humidification estimates were employed as a good practice indicator and the humidification action of the NGS in the year 2015 was checked for over-consumption periods in a year. It was observed that 33% of the time, there was overconsumption related to humidification, especially during the winter months. Maximum overconsumption was experienced during October and November, where the NGS humidifier load exceeded the good practice mark by up to two times. The system identification model of the NGS was tested with excellent accuracies of up to 99% correlation between predicted results and the actual recorded data. It is also concluded that ANNs are able to work with limited amount of building systems data (real data) readily available from the building management. The study further reinstates that the ANN based SI model can prove to be an ideal platform to investigate various optimisation strategies of the building operation in future, especially in the case of restrictive traditional building types where any retrofit solution needs a strong scientific backing of guaranteed success before practical implementation. In future, work will be done to further strengthen the Humidity Day concept and test the case of dehumidification by further working on some of the assumptions. Furthermore, sub-metering at the NGS will provide accurate data to help validate the findings, especially, the energy consumed by chillers and humidifiers during the winter months will give a required justification for the dehumidification figures obtained.Item Spatial and temporal controls on the development and evolution of the Tanzanian continental margin(Heriot-Watt University, 2017-02) Sii How Theng, Pollux; Underhill, Professor John; Jamieson, Doctor RachelThe East African seaboard has historically been considered to be a passive continental margin formed following rifting and continental break-up in the Middle Jurassic. Whilst much of the margin conforms to the standard passive margin model of pre-, syn- and post-rift sequences and a rift-drift subsidence history, the occurrence of anticlines forming the core to the islands of Zanzibar and Pemba attest to a more complicated tectonic evolution. Regional interpretation of a grid of high fidelity 2D and 3D seismic data, including a subset of long-offset, deep lines provides new insights into the margin’s crustal structure and shows geometries not normally attributed to passive margin development. These comprise a gently folded seabed, bedrock subcrop, a series of angular unconformities in the shallow section and an underlying zone of intense deformation associated with contractional reactivation of a precursor normal fault. This is consistent with the margin having undergone a hitherto unrecognized phase of structural inversion in the Neogene. Likewise, inversion and transpression structures are recognised offshore along NNW-SSE striking lineaments such as the Davie-Walu Trough, documenting additional contractional phases during the Cretaceous. Inboard of the zone of structural inversion, the Pemba Channel represents a protected remnant of extension and is still influenced by an E-W extensional regime, something that is substantiated by surface GPS data and earthquake focal mechanisms. The short-lived compressional events are envisaged to be related to external horizontal forces and far-field stresses associated with regional tectonism, particularly within the East African Rift System. However the crustal structure and basement fabric also play a role in the localisation of these stresses. Crustal identification along the margin supports lineaments set up during the initial NNW-SSE extension and N-S dextral southwards motion of Madagascar which may have reactivated under appropriately directed stress.Item CO2 capture and storage from power plant flue gas using gas hydrate-based technologies(Heriot-Watt University, 2019-08) Hassanpouryouzband, Aliakbar; Tohidi Kalorazi, Bahman; Yang, JinhaiThe climate system is changing globally, and there is substantial evidence that subsea permafrost and gas hydrate reservoirs are melting in high-latitude regions of the Earth, resulting in large volumes of CO2 (from organic carbon deposits) and CH4 (from gas hydrate reserves) venting into the atmosphere. As one of the main contributors to global climate change, power plants produce a substantial proportion of global anthropogenic CO2 emissions. Here, we developed techniques to capture and storage CO2 (CCS) present in power plant flue gases based on gas hydrate technologies. First, we experimentally measured the thermodynamic properties of different flue gases, followed by modelling and tuning the equations of states. Second, we proposed injection of flue gas into methane gas hydrate reservoirs as an option for economically sustainable production of natural gas as well as CCS. The optimum injection conditions were found and reaction kinetics was investigated in realistic conditions and well characterised systems. Third, kinetics of flue gas hydrate formation for both the geological storage of CO2 and the secondary sealing of CH4/CO2 release in one simple process was investigated, followed be thoroughly investigation of hydrate formation kinetics using a highly accurate in house developed device. Finally, effect of the proposed methods on permeability and mechanical strength of the geological formations was investigated.Item Multi-fidelity deep residual recurrent neural networks for uncertainty quantification(Heriot-Watt University, 2019-02) Kani, J. Nagoor; Elsheikh, Doctor Ahmed H.; Doster, Doctor FlorianEffective propagation of uncertainty through a nonlinear dynamical system is an essential task for a number of engineering applications. One viable probabilistic approach to propagate the uncertainty from the high dimensional random inputs to the high-fidelity model outputs is Monte Carlo method. However, Monte Carlo method requires a substantial number of computationally expensive high-fidelity simulations to converge their computed estimations towards the desired statistics. Hence, performing Monte Carlo high-fidelity simulations becomes computationally prohibitive for large-scale realistic problems. Multi-fidelity approaches provide a general framework for combining a hierarchy of computationally cheap low-fidelity models to accelerate the Monte Carlo estimation of the high-fidelity model output. The objective of this thesis is to derive computationally efficient low-fidelity models and an effective multi-fidelity framework to accelerate the Monte Carlo method that uses a single high-fidelity model only. In this thesis, a physics aware recurrent neural network (RNN) called deep residual recurrent neural network (DR-RNN) is developed as an efficient low-fidelity model for nonlinear dynamical systems. The information hidden in the mathematical model representing the nonlinear dynamical system is exploited to construct the DR-RNN architecture. The developed DR-RNN is inspired by the iterative steps of line search methods in finding the residual minimiser of numerically discretized differential equations. More specifically, the stacked layers of the DR-RNN architecture is formulated to act collectively as an iterative scheme. The dynamics of DR-RNN is explicit in time with remarkable convergence and stability properties for a large time step that violates numerical stability condition. Numerical examples demonstrate that DR-RNN can effectively emulate the high-fidelity model of nonlinear physical systems with a significantly lower number of parameters in comparison to standard RNN architectures. Further, DR-RNN is combined with Proper Orthogonal Decomposition (POD) for model reduction of time dependent partial differential equations. The numerical results show the proposed DR-RNN as an explicit and stable reduced order technique. The numerical results also show significant gains in accuracy by increasing the depth of proposed DR-RNN similar to other applications of deep learning. Next, a reduced order modeling technique for subsurface multi-phase flow problems is developed building on the DR-RNN architecture. More specifically, DR-RNN is combined with POD and discrete empirical interpolation method (DEIM) to reduce the computational complexity associated with high-fidelity subsurface multi-phase flow simulations. In the presented formulation, POD is used to construct an optimal set of reduced basis functions and DEIM is employed to evaluate the nonlinear terms independent of the high-fidelity model size. The proposed ROM is demonstrated on two uncertainty quantification test cases involving Monte Carlo simulation of subsurface flow with random permeability field. The obtained results demonstrate that DR-RNN combined with POD-DEIM provides an accurate and stable ROM with a fixed computational budget that is much less than the computational cost of standard POD-Galerkin ROM combined with DEIM for nonlinear dynamical systems. Finally, this thesis focus on developing multi-fidelity framework to estimate the statistics of high-fidelity model outputs of interest. Recently, Multi-Fidelity Monte Carlo (MFMC) method and Multi-Level Monte Carlo (MLMC) method have shown to significantly accelerate the Monte Carlo estimation by making use of low cost low-fidelity models. In this thesis, the features of both the MFMC method and the MLMC method are combined into a single framework called Multi-Fidelity-Multi-Level Monte Carlo (MFML-MC) method. In MFML-MC method, MLMC framework is developed first in which a multi-level hierarchy of POD approximations of high-fidelity outputs are utilized as low-fidelity models. Next, MFMC method is incorporated into the developed MLMC framework in which the MLMC estimator is modified at each level to benefit from a level specific low-fidelity model. Finally, a variant of deep residual recurrent neural network called Model-Free DR-RNN (MF-DR-RNN) is used as a level specific low-fidelity model in the MFML-MC framework. The performance of MFML-MC method is compared to Monte Carlo estimation that uses either a high-fidelity model or a single low-fidelity model on two subsurface flow problems with random permeability field. Numerical results show that MFML-MC method provides an unbiased estimator and show speedups by orders of magnitude compared to Monte Carlo estimation that uses a single high-fidelity model.Item Phase connectivity in pore-scale networks and capillary entry conditions(Heriot-Watt University, 2019-07) Petrovskyy, Dmytro; Jiang, Assistant Professor Zeyun; Van Dijke, Associate Professor Rink; Geiger, Professor SebastianQuasi-static pore-network modelling is a numerical approach that estimates multi-phase flow properties, such as capillary pressure and relative permeability functions in representative digital models of permeable media, the pore-scale networks. The present dissertation introduces substantial improvements to the conventional workflow and methodology of modelling of immiscible capillary displacement in pore-scale networks. The most significant advancement of this research is the development of a novel algorithm, that introduces a highly efficient approach to interrogate the phase connectivity and execute its alteration following pore-scale displacements in simulation of two-phase drainage and imbibition processes. The main disadvantage of a conventional implementation of the phase connectivity algorithm is the poor scalability of simulation time with increasing model size due to the inefficiency of the phase connectivity interrogation. The proposed solution demonstrates a practical speed-up by at least two orders of magnitude compared to all other existing implementations. Application of our algorithm allows for routine simulation of large models, which may integrate multiple scales of heterogeneity and capture representative elementary volumes comprising millions of pores. Robust sensitivity studies become feasible to evaluate the impact of uncertainty in multi-phase flow behaviour. Additionally, this thesis proposes a new method for the numerically precise estimation of capillary entry conditions in pore throats of arbitrary geometry and wettability. The newly estimated results show a considerable deviation from standard approximations characterised by regular simple shapes. Results demonstrate that a major concern arises when an approximated shape requires averaging of non-uniform wettability distribution of the original shape.