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Constraining diagenetic timings, processes and reservoir quality in igneous-affected basinsClark, Samantha Jean January 2014 (has links)
As the demand for hydrocarbons increases, more complex, non-conventional plays have been targeted in volcanic margin settings. Consequently, it is important to understand the role igneous rocks have in affecting hydrocarbon systems. This is particularly relevant to the Rosebank Field, offshore UK Continental Shelf, North Atlantic. The field was discovered in 2004 with the 213/27-1z well and encountered Palaeogene volcanic rocks interbedded with siliciclastic and volcaniclastic rocks, representing a brand new play type. Three appraisal wells were drilled and encountered good quality light oil (37° API) with drill steam tests achieving ~ 6000 STB per day (Duncan et al., 2009). Initially four companies had a stake in the field; Chevron (40%), Statoil (30%), OMV (20%) and Dong (10%) however in 2011, OMV bought out Statoil leaving them with a 50% stake. Chevron remain the operators. The importance of volcaniclastic sediments within these sequences has previously been overlooked and so a better understanding of how these rocks behave during burial is essential. This research quantitatively characterises and assesses the reservoir potential of a range of volcaniclastic and siliciclastic sedimentary rocks within such basins. The Rosebank Field comprises a range of volcaniclastic lithic arenites and lava flows interbedded with sublithic arenites and quartz arenites. However samples could only be taken from limited the limited cores. This made interpreting 3D architecture difficult and therefore it was decided that a onshore analogue was required. The Staffa Formation of the Palaeogene Mull Lava Field, NW Scotland, provides an excellent analogue to the Rosebank Field within the Faroe-Shetland Basin. It comprises basaltic lava flows interbedded with a variety of volcaniclastic and sedimentary rocks. A range of rock types occur within the Staffa Formation, including vent-proximal pyroclastic rocks, such as massive scoria rich tuffs to re-worked volcaniclastic lithic arenites to vent-distal facies where the siliciclastic component begins to dominate, such as quartz arenites. The Staffa Formation has therefore, been compared and contrasted to the Rosebank rocks to better understand composition, burial history and reservoir potential. Detailed characterisation of the volcaniclastic rocks has been undertaken using a variety of analytical techniques (optical microscopy, SEM and XRD), and demonstrates that volcanic material in potential reservoir rocks may significantly reduce their reservoir quality. Proximal pyroclastic rocks, which can have reasonably good porosity and permeability at the surface, degrade to non-reservoir values at shallow depths (<1km), as reactive volcanic components alter to both grain-coating and pore-filling clays during diagenesis. This process dominates diagenesis meaning that it only requires small proportions of volcanic material to be incorporated within a sediment to destroy its porosity. In some cases, alteration is so severe that the original rock textures and clast outlines are lost, making the rock difficult to identify. Several generations of pore-filling and grain-coating clays, formed from the alteration of volcanic glass, including gel and fibrous palagonite, Fe-smectite and chlorite, have been identified in the volcaniclastic rocks samples from both the Rosebank core and the Staffa Formation. The nature of the volcanic material plays an important role in a rock’s ability to retain reservoir quality. Factors such as the composition, shape and grain size of volcanic clasts in these rocks affect how the sediment behaved during diagenesis. Spatter bombs and scoria, for example, react differently clasts derived from lava. Labile volcanic ash shards that underwent minimal surface reworking altered to fibrous clay, and were then flattened and moulded around framework grains during diagenesis and burial. This reduced the local porosity and permeability in the rocks. Clay alteration of weathered basaltic clasts resulted in the development of pseudomorph grains that preserved the original grain structure and had only a minimal effect on surrounding pore throats. Clay formation in these rocks was extremely heterogeneous and highly dependent on the immediate grain-scale mineralogy. Clay phases developed during early diagenetic stages blocked or altered later fluid pathways, which led to an extremely patchy diagenetic mineralogy. Rocks inferred to be located at more distal locations from the vent have higher proportions of siliciclastic components and somewhat simpler paragenetic sequences that are characterised by carbonate and silicic cements and minimal authigenic clays. Oxygen and hydrogen isotopic data provide constraints on pore water chemistry and temperatures during diagenesis. Together, these data have been used to determine the diagenetic histories of the Rosebank Field and Staffa Formation, and enabled the development of a conceptual model to determine the threshold at which volcaniclastic rocks are no longer viable as petroleum reservoir rocks. The model shows that volcaniclastic rocks containing more than 10% volcanic clasts are likely to have very poor reservoir quality at depth. However, this is dependent on a number of factors such as clast size, clast type, depositional setting, sorting, pore water composition and timing. These data will be of use in the assessment of potential plays in volcanic rifted margins worldwide.
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Aspects of the tectonics of the Greater Caucasus and Western South Caspian BasinAlburki, Abduelmenam January 2015 (has links)
The main objectives of this project are to (a) understand the relationship between climate, topography and the tectonics in the Greater Caucasus belt, (b) construct regional geological cross-sections showing major stratigraphic sequences and structures along the belt using the focal mechanisms of the earthquakes events, (c) evaluate the evolution and development of a single fold structure (Yasamal anticline) and (d) investigate strain accommodation mechanisms using 3D Move to unfold the Yasamal structure. Topographic variations were investigated to understand the interplay between topography, climate and the tectonics of the Greater Caucasus range and compare the findings with other active and inactive belts (Pyrenees, Northern Tibetan Plateau and Himalayas). There is a correlation between elevation changes and climate along the Greater Caucasus belt, where the gradual reduction of the mean altitude, has a close relationship with a wetter climate, and the sharper altitude decrease with a drier climate. And the elevation changes are strongly correlated with the Moho depths underneath the region. The relief along the belt is extremely high, with a strong correlation between the high relief and the large thrusts in the region. And the relief of the eastern part is slightly low compared with the western part of the belt, even though the eastern part is more active than the western part. The structural study undertaken at regional scale for the Caucasus belt and the western side of the South Caspian Basin gave insights on the style of deformation in the basin and the evolution of the Greater Caucasus belt and the preferred distribution, geometry and formation mechanism of the structural elements. The regional cross-sections along the Greater Caucasus were constructed and constrained by using focal mechanisms show that the belt is deformed by active thrust faults that dip inwards from the margins of the range where the northern thrusts are dipping south, and the southern thrusts are dipping to the north, these results have contrary to some previous models that emphasise only south-directed thrusting. The spatial arrangement, geometry and temporal evolution of spectacular kilometre-amplitude fold structures actively forming in Cenozoic sediments on the uplifted western margin of the South Caspian Basin are described and strain accommodation mechanisms established using 3D Move to unfold the Yasamal structure enabled a reconstruction of pre-folding templates and predictively model the fold-related deformation at small-scale. The 3D model of the Yasamal anticline shows that the anticline hinge has about 30° south-directed plunging. The area was characterized by a low rate of sedimentation and high rate of uplift in the Upper Pliocene. The minor structures (accommodating the overall strain in the anticline) are developed throughout the entire anticline. Compressional strain is present at the anticline hinge line, and the extensional strain dominates the anticline limbs. Suggesting potential extensional structures development in the anticline flanks, which correspond with the field observations in the Yasamal valley confirming that; the small normal faults are concentrated within the anticline flanks, and the contractional deformation bands along the hinge area of the anticline.
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Fault zone architecture, microstructures, deformation mechanisms and frictional behaviour of seismogenic, shallow-crustal, lithologically heterogeneous faultsBullock, Rachael Jane January 2015 (has links)
Earthquakes that rupture the Earth’s surface are typically the most damaging and highlight the need for us to better constrain the style of deformation and frictional behaviour of fault zones in the shallow crust. This thesis presents two studies of natural, seismogenic, shallow crustal fault zones: 1) the Gubbio fault zone, which has been exhumed from 2.5-3 km depth and deforms a mixture of limestone and phyllosilicate-rich marly limestone; and 2) the Masada fault zone, which deforms near-surface, poorly lithified lake sediments. Field studies were complemented by low- and high-velocity rotary shear experiments to constrain the frictional behaviours of the naturally observed fault gouges under representative conditions. In addition, microstructural analyses of both naturally- and experimentally-produced fault rocks were performed in order to constrain the deformation mechanisms operating during fault slip. Our results show that the dominant deformation mechanisms operating within a fault zone, which are highly variable depending on environmental conditions such as depth, fault rock composition, fluid presence and composition, and strain-rate, will control: 1) fault zone architecture and therefore the distribution of seismicity; and 2) slip zone processes, which can subsequently affect the frictional behaviour of a fault, and also determine whether or not signatures of seismic slip are produced during rupture propagation. These are useful tools for geologists when trying to decipher the seismic history of natural faults. Frictional behaviour, in terms of the likelihood of rupture propagation through the shallow crust, is also found to vary significantly as a function of the aforementioned environmental conditions. A fuller knowledge of spatial, and possible temporal, variations in fault zone properties is therefore essential if more accurate earthquake forecasting models and assessments of their associated hazards are to be produced.
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Becoming disabledSellick, Jayne Margaret January 2014 (has links)
This thesis examines the becoming of disabled people’s identities, illustrating the multiple and complex temporalities that shift and move in flux as disabilities, health conditions and illnesses change over time. Understanding disability as an unfolding process of continuous change, the thesis forwards the concept of ‘becoming disabled’ as tying together disabled people’s lived and embodied experiences. An unfolding participatory qualitative research methodology was developed with eight participants and their partners. Four methods were chosen by participants to explore their experiences: drawing participatory timelines, taking photographs through photovoice, talking in conversations and writing diary entries. The research process itself moved back and forth, overlapping and churning through cycles of participation, action and reflection, shaping the subsequent findings, which are arranged under four key themes. ‘Becoming emotional’ explores the gendered and emotional temporalities of events, such as diagnosis, accident and injury, to everyday acts that shape the future. ‘Becoming well’ illustrates the affective capacity of material items to facilitate day-to-day and lifelong recoveries. ‘Becoming mobile’ discusses the pace, speed and rhythm of walking and wheeling. ‘Memories’ of disability, health conditions and illnesses continue to unfold, shaping new possibilities and new futures. The thesis concludes that becoming disabled is an underlying, always present and unfolding process of continuous change, which differs to the fixed and categorical basis of ‘being disabled’ which has characterised much research. Becoming disabled is always reaching forward and never complete, emphasising the intricacies of time, the temporalities, the moments, the transitions and the trajectories of becoming, in everyday life and across the life course. The research sought to examine the everyday practices and processes that shape disabled people’s identities; and to explore the role of the past, the present, and the future in disabled people’s lives. Suggestions are made for future research.
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Groundwater and geotechnical controls on landslide mechanisms of coastal cliffs formed in glacial tillNawawitphisit, Sasiwimol January 2014 (has links)
Landslides behave in a complex manner especially in terms of the relationship between groundwater variation and the mechanisms of movement; a relationship that remains poorly understood. The aim of this research is to improve the understanding of landslide movement patterns for coastal cliffs. The objectives are (1) to understand controls on landslide initiation; (2) to evaluate landslide movement patterns so as to explain the development to failure and their mechanisms; and (3) to investigate the hysteresis relationship between groundwater and displacement rate. Field monitoring has been undertaken at Upgang, a cliff formed in glacial till in North Yorkshire, UK (54.29° N and 0.38° W) for 30 months between 2010 and 2012. The monitored section extends 250 m along the coast and is 30 m high. The characteristics of the cliff face and its deformation over time were monitored monthly by terrestrial laser scanning. The landslide complex displays seasonal movements, associated with rotational failures, sliding and deterioration of the failed mass into a complex of mudslides. Movement is dominated both by groundwater variations resulting from precipitation, and marine cutting of the cliff toe. Data from a reactivating landslide, situated at the upper till section of the cliff, was selected to characterise post-failure change. The high spatial and temporal resolutions of the monitoring undertaken in this research allow these processes to be better understood. Uniquely, this study combines three detailed datasets including terrestrial laser scanning, in-situ monitoring and rigorous laboratory testing to explore the controls on the nature and style of landslide movement. The results demonstrate that reactivation of the landslide occurred in phases of accelerated (0.2 – 6.27 mm/hr), slow (< 0.2 mm/hr) and negligible movements, which were found to be influenced by the fluctuation of groundwater. A complex relationship has been found at the reactive shallow landslide, where the onset of accelerated movements corresponds to an increase in groundwater at the landslide base. Two types of hysteresis patterns, both clockwise (Strain hardening) and anti-clockwise (Strain softening), relating groundwater and displacement rate, were observed. The key controlling mechanism appears to be plastic deformation. The varied velocities are dependent on the stress state controlled by both rate of change in groundwater and absolute groundwater level. The intensity of rainfall has a significant effect on the style of movement. The results have wider implications for understanding the controls on landslide movement in coastal cliffs and reactivation landslides.
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Direct and indirect effects of flood basalt volcanism on reservoir quality sandstoneGrove, Clayton January 2014 (has links)
This thesis describes the direct diagenetic effects on porous clean sand substrate due to the emplacement of basalt lava flows. The thesis also describes the effects of the emplacement of basaltic dykes and sills into clean porous sandstone. The primary dataset comes from the Cretaceous Etendeka Group, NW Namibia, where the Etendeka Flood Basalts (and associated subsurface plumbing system) interacted with the aeolian Twyfelfontein Formation sandstone. Secondary datasets from the recent Rekjanes Peninsular basalts, Iceland; the Miocene Columbia River Flood Basalt province and the Miocene Snake River Basalts, NW USA are used to constrain the direct effects of lava on substrates in a variety of palaeoenvironmental conditions. The thesis makes use of a number of analytical techniques including: petrography, scanning electron microscopy, image analysis, X-ray diffraction, X-Ray fluorescence, stable isotope spectroscopy (δ18 O and δ13 C) and gas permeability (Hasler and probe). The findings of this work constrain the degree of porosity reduction in clean sandstones due to intrusion emplacement over a complete range of thermal regimes, controlled by the magma flow pathways and duration. The effects range from mild hydrothermal activity and compaction through to intense pyrometamorphism, sediment melting and segregation. Beneath lava flows, the degree of porosity loss is determined by palaeoenvironment (specifically the availability of free water), the lava thickness and the substrate composition. Together the geometries of the igneous components (intrusions and extrusive flows) of the Etendeka Group compartmentalise the sedimentary components (Twyfelfontein Formation), which can be traced due to their effects on hydrothermal activity. The main compartment forming lithologies are vertical-subvertical intrusions, with the lava flows being a minor contributor. The diagenesis during hydrothermal activity was found to be a natural sequestration mechanism of CO2 derived from igneous activity as well as a highly compartmentalised porosity degradation mechanism.
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Recent Central American and low latitude climate variability revealed using speleothem-based rainfall proxy records from southern BelizeRidley, Harriet Elizabeth January 2014 (has links)
Comprehensive assessment of recent tropical climate variability is essential in order to understand the full spatial expression of climate change in the context of long term climate variability. This requires highly resolved and precisely dated tropical proxy records which include the critical transition from the pre-industrial to industrial eras. Speleothem provide highly-resolved and well preserved climate signals and are particularly valuable in tropics where few alternative high resolution records are available. This thesis presents a comprehensive study of recent Central American and low latitude climate variability through assessment of two highly resolved speleothem stable isotope based rainfall proxy records from Yok Balum Cave, southern Belize. The YOK-G stalagmite δ13C record has a bi-monthly resolution and robust chronology permitting the inference of palaeo-seasonality as well as intra annual rainfall variations over the last 453 years. The record strongly suggests that volcanic aerosol injections into the Northern Hemisphere atmosphere result in southward Intertropical Convergence Zone (ITCZ) repositioning, and firmly implicate anthropogenic aerosol emissions as having caused 20th Century rainfall reductions in the northern tropics. The YOK-I stalagmite δ13C record provides a bi-annually resolved correlate records of North Atlantic Oscillation for the last 2000 years. Links between high latitude explosive volcanism and repositioning of the ITCZ are further investigated with emphasis on the subsequent impact of observed North Atlantic Oscillation (NAO) phases. High latitude eruptions are compellingly linked to negative NAO circulatory patterns in the North Atlantic thereby providing new insight into atmospheric mechanics of the North Atlantic. Cave monitoring data provides essential background information on cave environmental variables which could modify climate signals preserved within speleothem carbonate, precluding or complicating interpretations. Using remote monitoring techniques the cave ventilation dynamics and hydrology at Yok Balum are characterised, thereby helping to put the speleothem geochemical data discussed into correct environmental context.
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Fuelling the dragon : a geopolitical economy of natural gas transition in ChinaLeung, Chun Kai January 2014 (has links)
To tackle its coal-induced air pollution and carbon mission problems, the Chinese government has sought to increase the share of natural gas in its fuel mix to 10 percent by 2020. The gasification of the fuel mix requires the gasification of the country’s energy supply chain, which implies transitions in infrastructures, actors and institutions throughout the chain. This dissertation adopts the global production networks (GPN) approach to evaluate how this form of energy transition will unfold functionally, organisationally, institutionally and politically in and across space. Specifically, it assesses the relational landscape of China’s energy governance, and its implications for gas acquisition, distribution and consumption. It finds: (i) the governments, national oil companies and Chinese Communist Party does not behave like a coherent monolith; instead a range of state actors and institutions have defined the structure of China’s gas production network; (ii) China’s state-led expansion of gas infrastructure is surprisingly effective despite the fragmented governance structure; (iii) national oil companies are seeking further vertical integration at the expense of the prospects of independent downstream players; (iv) China’s gas extraction, import, distribution and consumption can only be understood in relation to one another; (v) any ‘strategic coupling’ between international oil companies and China’s regional gas assets and institutions is conditional, and the window of opportunity is wider in the unconventional gas extraction and downstream distribution; and (vi) future development of gas consumption is institutionally uncertain. This research also, via the case of the gasification in China, demonstrates the utility of GPN approach for understanding energy transition.
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The production, practice and potential of 'community' in Edinburgh's Transition Town NetworkAiken, Gerald January 2014 (has links)
‘Community’ is increasingly seen as a solution to the environmental challenge faced in the UK. This original work critically evaluates schemes utilising ‘community’, focusing on those adopting the Transition Town Network (TTN) name, and those funded through the Climate Challenge Fund (CCF). It is based on qualitative, participative, empirical research with three of Edinburgh’s Transition Town Network groups and eighteen of their initiatives. This thesis charts the production of ‘community’ within these groups, set against the background of ‘community’ rhetoric both within TTN in general, and increasingly UK environmental policy more widely, specifically in the CCF. It then assesses what ‘community’ means – and has come to mean – in this context. ‘Community’ as a term for government capture of innovative political collectives, or as a progressive mobilising force, uniting diverse actors through small-scale belonging, are critically assessed in turn. The thesis argues that the concept of zuhanden – ‘ready-to-hand’, drawn from phenomenology – offers a fruitful way to understand ‘community’. Doing so emphasises and captures the hitherto neglected way in which ‘community’ is acquired, rather than sought. Building on this analysis the thesis then interrogates how ‘community’ as acquired rather than sought is envisioned and enacted in three of Edinburgh’s TTN groups. The thesis argues that this is closely intertwined with the way in which time is understood by such groups; the notion of ‘possible futures’ which are posited by ‘transition’. This is inherently connected to the groups’ view of space, and has implications for how they view and achieve success, and the tensions this creates with surrounding actors. It concludes with an assessment of the barriers or opportunities remaining for such ‘community’ initiatives. Through these issues, the thesis addresses the potentially irreconcilable tensions that exist between the CCF and TTN, and offers valuable lessons for ‘community’ groups in future.
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Domesticating infrastructure : Mumbai's middle class housing and rainwater harvestingButton, Catherine Myrena January 2014 (has links)
Housing is no longer merely a site of resource consumption, but also supplier of decentralised ‘green’ resources for Mumbai’s middle classes and rainwater harvesting is pivotal to this shift as the first major environmental intervention. This thesis aims to assess how Mumbai’s middle classes are responding to water shortage and environmental change through domestic rainwater harvesting. Rainwater harvesting is mandatory in newly constructed buildings and retrofits are becoming increasingly popular as the municipality promotes water saving initiatives. The responsibility for securing water resources in Mumbai’s middle class households has thus been shifted onto the residents themselves at the same time as they strive to secure and improve their lifestyles. This research draws on fieldwork in Mumbai from 2009 to 2011 to explore how rainwater harvesting is being governed, assembled and practiced by the rapidly growing but under-researched middle classes. A socio-technical framework is used to analyse the findings and this thesis draws three main conclusions: Firstly, housing is being repositioned as a water supplier, and thus a site for governing services, promoting middle class responses to shortage and allowing the municipality to roll back provision. Secondly, the domestication of water supplies through rainwater harvesting can accelerate the uptake of other environmental technologies within residential buildings by creating apertures in the socio-technical transition. Thirdly, rainwater harvesting facilitates the performance of middle class lifestyles by securing constant water supplies but servants can distance residents from resource use and influence uptake and effectiveness of these decentralised environmental services. Therefore, if these complexities are acknowledged, the domestication of water infrastructure through rainwater harvesting has the potential to open up Mumbai’s homes to become more sustainable.
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