Energy, Geoscience, Infrastructure and Society
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Item Pore-scale 3D imaging of hydrogen storage in rocks(Heriot-Watt University, 2024-05) Jangda, Zaid Zaffar; Singh, Associate Professor Kamaljit; Busch, Professor Andreas; Geiger, Sebastian;Escalating concerns over climate change have accelerated the need to transition towards cleaner energy sources, such as hydrogen. For a sustainable hydrogen economy, effective storage solutions are important. Subsurface porous rocks offer a promising solution, capable of storing substantial volumes of hydrogen for varying durations to meet fluctuations in energy demand. However, a comprehensive understanding of hydrogen flow and entrapment within these rocks, particularly under reservoir conditions, remains a significant challenge. In this thesis, X-ray micro-tomography is used to investigate the pore-scale distribution, trapping, and recovery of hydrogen under subsurface conditions. Through 3D flow-visualisation experiments on sandstone rocks, initial and residual hydrogen saturations are quantified, providing an assessment of the hydrogen storage capacity and recovery efficiency of these rocks. Additionally, the potential dissolution of hydrogen in brine is observed, a phenomenon that could contribute to hydrogen loss during storage and production. Furthermore, the influence of small-scale rock heterogeneity is investigated through experiments on a layered rock. These experiments highlight how subtle rock structure variations impact hydrogen displacement, leading to reduced storage capacity upon injection and significant hydrogen trapping during production. Such findings stress the pivotal roles of pore-scale processes and small-scale rock heterogeneity in the design, selection, and implementation of subsurface hydrogen storage systems. Moreover, a comparison of experimental results with a pore-network model reveals that simplistic models fall short in accurately predicting hydrogen flow and trapping in real rocks, particularly heterogeneous media. This highlights the importance of experimental research, such as this study, in advancing our understanding and optimisation of subsurface hydrogen storage.Item Fracture in reinforced concrete: computational and analytical studies(Heriot-Watt University, 1999-12) Gastebled, Olivier J.; May, Professor Ian M.Please refer to PDF.Item An investigation into the influences upon and determinants of perceived quality achievement in the management of construction projects by multivariate analysis(Heriot-Watt University, 1988-06) Sani, Habu; Torrance, Professor Victor B.; Cheesman, Peter G.Abstract unavailable please refer to PDFItem Prediction of sulphate scaling tendency and investigation of barium and strontium sulphate solid solution scale formation(Heriot-Watt University, 1989-07) Yuan, Mingdong; Todd, Doctor A.C.Abstract unavailable please refer to PDFItem The influence of design team communication content upon the architectural decision making process in the pre contract design stages(Heriot-Watt University, 1987-08) Wallace, W. A.; Kelly, J.No abstract available please refer to PDFItem Decision support and risk management system for competitive bidding in refurbishment work(Heriot-Watt University, 1990-06) Teo, Ho PinNo abstract available refer to PDFItem The design and management of tanks for the culture of turbot (Scophthalmus maximus (L))(Heriot-Watt University, 1990-03) Cripps, Simon Johathan; Poxton, MikeAbstract not available please refer to PDFItem A conceptual procedural framework for effective scheduling to enhance efficient use of construction resources on the jobsite(Built Environment, 2009-04) Efole, Friday E.; Kaka, Professor AmmarSelection of construction methods, scheduling, site layout and component procurement arrangement affect efficiency of operations on the jobsite. Efficiency has been previously measured by such parameters as; budget, on time completion and meeting specification standards. Little attention has been given to the interim processes which create these. Efficiency in man- and machine-hour management may translate to cost and time gains and enhanced quality. The study reported recognises that there are numerous aspects to the question of efficiency of operations. To focus the study and narrow the scope to a manageable size, the issues of efficiency that can be addressed in the scheduling process are those considered. Extensive and thorough literature search identified guidelines for effective construction scheduling. Empirical data were collected following these guidelines to develop a scheduling procedure aimed at making the process more effective and which may enhance efficient use of construction resources on the jobsite. The developed framework show that activity criticality based on time analysis alone is a necessary condition but not usually sufficient to declare an activity critical. Other tasks not on the critical path which have very high delay potential should be considered. Therefore though the study does not out rightly refute the idea of criticality based on time analysis alone, it adds to it that if criticality means those things that should be done so as to progress the works to a scheduled finish, criticality should be re-assessed to include several other tasks not hitherto identified on the critical path.Item Hydrates in sediments : their role in wellbore/casing integrity and CO2 sequestration(Heriot-Watt University, 2009-12) Salehabadi, ManoochehrGas hydrates have attracted much interest among researchers recently because of their wide range of applications. The impact of natural gas hydrates in subsea sediments on the development of conventional hydrocarbon reservoirs in deep offshore and the potential role of CO2 hydrates as a secondary safety factor in subsurface storage of CO2 are the key areas in this thesis. Several experiments were conducted on synthetic samples containing methane hydrate with different hydrate saturations to measure their geophysical properties, mechanical properties and understand their mechanical behaviour at realistic conditions. A numerical model was also developed with ABAQUS (a finite element package) to investigate the casing stability of the wellbore drilled in gas hydrate bearing sediments in deep offshore environments using the measured properties of gas hydrate bearing sediments under different scenarios. The role of hydrates in subsurface storage of CO2 was studied using a unique experimental set-up by simulating geothermal temperature gradient. The objective was to investigate whether CO2 leaked from subsurface storage sites can be converted into hydrates, providing a secondary seal against further CO2 leakage to ocean/atmosphere.Item Inversion for reservoir pressure change using overburden strain measurements determined from 4D seismic(Heriot-Watt University, 2009-11) Hodgson, NeilWhen significant pore pressure changes occur because of production from a hydrocarbon reservoir the rocks both inside and outside of the reservoir deform. This deformation results in traveltime changes between reflection events on timelapse seismic data, because the distance between reflection events is altered and the seismic velocity changes with the strain. These traveltime differences are referred to as time-lapse time shifts. In this thesis, time-lapse time shifts observed in the overburden are used as an input to a linear inversion for reservoir pressure. Measurements from the overburden are used because, in general, time shift estimates are more stable, the strain deformations can be considered linear, and fluid effects are negligible, compared to the reservoirlevel signal. A critical examination of methods currently available to measure time-lapse time shifts is offered. It is found that available methods are most accurate when the time shifts are slowly varying with pressure and changes in the seismic reflectivity are negligible. While both of these conditions are generally met in the overburden they are rarely met at reservoir level. Next, a geomechanical model that linearly relates the overburden time-lapse time shifts to reservoir pressure is considered. This model takes a semi-analytical approach by numerical integration of a nucleus of strain in a homogeneous poroelastic halfspace. Although this model has the potentially limiting assumption of a homogenous medium, it allows for reservoirs of arbitrary geometries, and, in contrast to the complex numerical approaches, it is simple to parameterise and compututationally efficient. This model is used to create a linear inversion scheme which is first tested on synthetic data output from complex finite-element model. Despite the simplifications of the i inversion operator the pressure change is recovered to within ±10% normalised error of the true pressure distribution. Next, the inversion scheme is applied to two real data cases in different geological settings. First to a sector of the Valhall Field, a compacting chalk reservoir in the Norwegian Sea, and then the Genesis Field, a stacked turbidite in the Gulf of Mexico. In both cases the results give good qualitative matches to existing reservoir simulator estimates of compaction or pressure depletion. It is possible that updating of the simulation model may be assisted by these results. Further avenues of investigation are proposed to test the robustness of the simplified geomechanical approach in the presence of more complex geomechanical features such as faults and strong material contrasts.