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In an age of increasing energy demand it is clear that we must utilise our energy resources as efficiently as possible. Current oil extraction methods only recover in the region of a third of the oil in a reservoir. Presently oil is recovered through primary methods (pressure differentials) and secondary methods (water-flooding). However, it has been shown that incremental oil recovery beyond secondary methods can be achieved via using water floods of decreased salinity. The aim of this research is to bring clarity to the fundamental mechanisms behind low-salinity enhanced oil recovery (EOR), a technique where sea water, partially desalinated, is used to push increasing amounts of crude oil from existing, and future, oil reservoirs, increasing the reservoir lifetime and overall production. In this thesis, the key mechanisms driving low-salinity EOR have been examined with atomic resolution using classical molecular dynamics (MD) simulations. Simulations have focussed on modelling the three-phase properties of clays (montmorillonite and kaolinite) with model oil compounds (containing decane, decanoic acid and decanamine) at varying salt concentrations of brines (NaCl and CaCl2). The key result presents that clay minerals play an important role in the phenomenon of low-salinity EOR. The oil-wettability of a clay mineral surface is dictated by several factors, including: (a) the surface charge density of the mineral; (b) the nature of the charge balancing cation (monovalent vs divalent); (c) the amount of polar components within the oil phase; (d) the salt concentration of the surrounding flood.

Due to the current oil consumption increase, deposits have decreased drastically. Engineers are constantly pushing the limits in order to drill deeper, convey oil further or build more efficient and sturdy pipelines. In an e.ort to obtain this rare ressource, companies are sometimes forced to install pipelines in extreme conditions and isolated terrains to exploit untouched oil deposits. If the structural designs of these devices have come to an agreement, internal phenomena occuring during the oil transport, are, currently not fully understood. In particular, droplets distribution evolution along with freezing events are the two main mechanisms responsible for efficiency loss of pipelines under extreme conditions. The aim of this work is to improve the current knowledge on these phenomena. For many years, oil industry has focused on expensive experiments to better apprehend complex flow phenomena. A promising alternative, computational fluid dynamic (CFD), has been used in this PhD to fill the gap of knowledge in this field of study. Two new single-fluid solidification solvers, an improved population balance model and a novel multi-fluid solidification model have been developed. These solvers have been implemented in an open-source CFD environment (OpenFOAM) to ensure universal acces and a potential extension to this work. It is shown that both single-fluid solidification solvers provide very good results when compared to experimental data. The maximum local discrepancies are evaluated below 20% for the worst case. The population balance model study performed in this PhD has identified important parameters, often under-looked. These findings have led to an improvement of the previous model close to 30% for the best case when compared to experimental results. The multi-fluid solidification model provides accurate ice formation rates (10% of maximal local discrepancies) when compared to experiments. The work presented in this thesis, describes, within the same CFD environment, solvers able to compute both droplet size and distribution evolution and solidification processes. They can be used separately or conjointly to perform the numerical analysis of the flow behavior under extreme conditions, improving the way such problems are currently tackled. They can also be enhanced further to deal with sligthtly di.erent research areas such as hydrates formations and corrosion events.

Geochemical studies have been carried out over copper-cobalt mineralization in the Kilembe Area, Uganda. The mode of occurrence end dispersion mechanisms of copper were investigated in the soils, ground-waters, surface waters end active stream sediments. In soils, the copper is mainly concentrated in the clay and silt size fractions, end rather more then half of the metal is associated with secondary iron oxides. Soil creep is active on the steep hill slopes end copper bearing soils enter the drainage vie the stream banks. Metal leeched from the soil by percolating rainwater is transported to the ground-water without apparently being re-precipitated in the lower horizons of the overburden. The solubility of copper in natural waters appears to be related to the pH and bicarbonate-sulphate content of the solutions. Shallow ground-waters ere acidic end contain low concentrations of bicarbonate compared to surface waters, which are neutral or alkaline, end generally contain high bicarbonate concentrations. The acidity end low bicarbonate concentrations of subsurface waters ere considered to be mainly due to the high partial pressure of carbon dioxide in soil air, end ground-waters ere apparently capable of dissolving larger concentrations of copper then surface waters. The increase in pH end bicarbonate (end the resultant decrease in saturation potential for copper) of surface waters is thought to be caused largely by the loss of carbon dioxide upon transition from the subsurface to surface environment. Ground-waters containing copper in excess of the saturation concentrations appropriate to the surface environment, precipitate the metal upon emergence into the atmosphere. The copper in stream sediments is concentrated mainly in the clay end silt size fractions. The metal is derived largely from eroded bank soils end, to e lesser extent, by precipitation from waters. Thus, the distribution of copper in the drainage is controlled by both mechanical end saline dispersion mechanisms. The results of these studies indicate that surface waters draining mineralization hove negligible drainage trains of ionic copper, but limited drainage trains of non-ionic copper were observed. However, extensive downdrainage dispersion trains of copper in the sediments were observed, end it is possible to detect the presence of mineralization occurring in the catchment areas of streams by analysing stream sediments for hydrochloric acid soluble metal.

There is growing fear that world oil reserves are depleting fast due to the current energy demand, and future energy needs. Recently, there has been a call for radical shifts in investment towards cleaner and more efficient energy technologies. However, most of these renewable energy alternatives are still at infant stages of research. Thus, the more conventional hydrocarbon oil is still the most logical option. Oil recovery efficiency is heavily influenced by the structure of void space that oil occupies within the reservoir rocks. In general, less than 50 % of oil is recoverable from the source rock, and thus the understanding of oil entrapment (bound volume index) is essential in prediction of economical potential of an oil reservoir. The bound volume index is the non-movable fluid volume in oil reservoirs. Reservoir rocks are chemically and geometrically heterogeneous. In this study, model catalyst support pellets with similar chemical and geometrical properties to oil reservoir rocks, but with more homogeneous chemistry were investigated. In this thesis, novel multi-technique approaches have been used to understand the transport relationships in porous media. The mechanisms of entrapment and distribution of the irreducible non-wetting phase within porous media was investigated with mercury porosimetry. Mercury entrapment is strongly dependent on the structural (voidage fraction, pore size, and pore size distribution) as well as on topological (connectivity and tortuosity) properties of porous media. The pore size distribution (PSD), a measure of pore length, and pore connectivity were determined by gas sorption. PGSE NMR was used to study the heterogeneity and tortuosity of the samples. In addition, PSGE NMR was used to study the kinetics of adsorption in porous media, and thus elucidate the relationships of liquid connectivity, and molecular exchange between liquid and vapour phases. In general, mercury entrapment occurred at larger mesopore radii, and was present at all experimental time-scales. In addition, mercury entrapment was found to increase with increased variance in the PSD. PGSE NMR kinetic studies revealed that tortuosity decreased with an increased liquid connectivity and there was enough evidence to suggest molecular exchange between the liquid and vapour phases. Furthermore, the tortuosity of fully saturated samples increased with an increased mercury entrapment.

gh European energy demands, the difference in prices amongst Europe and ambitious gas producers, have produced a scenario of high competition in a region that suffers a lack of fossil resources still required for energy generation. Therefore, other sources are under the scope of various countries to mitigate these issues. Shale gas is one fuel that presents a scenario that would decrease European dependence on imported gas. Although shale gas production is unlikely to give the energy security desired to the whole Europe, it would make a difference for the communities that will adopt it. However, shale gas has acquired a bad reputation with the public, mainly because of its extraction methods. This bad reputation is attributed to hydraulic fracturing, technology well-known as fracking, and its risks associated towards air and water pollution. Therefore, companies, institutions and governments are looking for other alternative methods of extraction with more environmentally friendly processes. Producing extensive high-pressure pulse waves at the base of the wellbore by using detonation is a promising potential technique for shale gas extraction. A fundamental study of deflagration to detonation transition using recirculated shale gas formation with pure oxygen as an oxidiser has been studied to design a system with lower DDT distance and higher pressure waves. Three proposed cases of UK shale gas composition were studied. Chemical equilibrium software GASEQ and chemical kinetic software CHEMKIN-PRO were used to estimate the product parameters. Results showed that the effect produced by diluents, such as carbon dioxide, are eliminated by the use of higher hydrogen content carbon-to-hydrogen species for the three cases proposed. OpenFOAM CFD was used to calculate the deflagration to detonation transition parameters in stoichiometric hydrogen air mixtures to evaluate different obstacle geometries on the transition phenomenon to improve the detonation process. The shape and layout of obstacles were found to have a significant effect on flame acceleration, and subsequent detonation propagation. The interaction of transverse pressure waves generated at the obstructions governs the propagation mechanism. The transverse waves and its frequency appear to play a pivotal role in supporting the detonation wave. H iv It was found that rectangular shape obstacles reduce the reaction time, while triangular ones achieved detonation with the minimum run-up distance. On the other hand, semicircular shape obstacles generate the highest pressure in a detonation tube. The outcome from numerical calculations and CFD were the guide to construct an experimental rig of 21.2mm diameter and 1500mm length tube with different obstacle configurations to demonstrate the concept of pulse detonation for shale rock cracking. Experimental work has been performed to determine the potential of shale gas production in the Dullais Valley, South of Wales. It was found through several tests using BS standard volatile analyses, Transmission Electron Microscopy and pyrolysis RockEval evaluation that the potential of extraction in this region is fair, with similar concentrations of pyrite but with low energy content compared to those resources located in the Midlands and Yorkshire. However, the use of controlled pulse detonation could be the ideal technology for extraction in Wales, as low sulphur (S) content will produce lower unwanted emissions, with a process that can promote opening of pores and further gasification of oil based molecular, with a subsequent increase in shale gas production, topic that requires further research. Finally, a 2-dimensional simulation was performed using ANSYS Parameter Design Language (APDL) to investigate the effect of pressure pulse generated by the detonation tube on a pre-crack. Results showed that the layer close to the applied load will be displaced, which means that it will be smashed. The maximum Von Mises stresses were found to concentrate at the perforating hole corners, while the region immediately after the crack tip is susceptible to compression stresses. The Same behaviour was found for the stress intensity factor. According to that, it is believed that the cracks will propagate diagonally from the perforating hole base. Therefore, the current work has theoretically demonstrated the technology for shale gas recovery, with an optimised geometry consistent of internal obstacles, for a region with potential for shale gas exploitation.

This thesis investigates the behaviours of iron(II) oxidation, iron(III) settling and total iron removal from ferruginous circumneutral, and to a lesser extent, acidic coal mine water discharges from across the globe. Comparisons are drawn between existing iron(II) oxidation and iron removal studies and new knowledge is developed in the area of iron(III) settling behaviour, iron removal rate-limiting steps and methods to examine the treatability of ferruginous circumneutral mine water. Measured iron(II) oxidation rates are shown to be higher in this study than previous authors’ work, which is likely to be due to higher concentrations of particulate iron(III) present in the mine water that acts to catalyse the oxidation reaction. The iron(III) settling rate constant is shown to be proportional to the initial total iron concentration, however it is also seemingly effected by the concentration of magnesium and calcium present in the mine water. Rates of total iron removal are shown to be in general linearly proportional to the initial total iron concentration due to the acidity of the mine water, and oxidation and settling rate limiting steps, however some data does lie off of the trendline, meaning that it would not be suitable to be used to predict final total iron concentrations. Additionally a small study on modelling of the settling lagoons to predict the outlet iron concentrations based upon the inlet conditions and hydraulics of the lagoon was conducted and compared to existing settling lagoon formulae to ascertain which was the most accurate in terms of correctly predicting the outlet iron concentrations.

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