Richard Shaw

Understanding the micro to macro behaviour of rock-fluid systems

Understanding how fluids flow through though rocks is very important in a number of fields. Almost all of the worlds oil and gas are produced from underground reservoirs. Knowledge of how they got where they are, what keeps them there and how they migrate through the rock is very important in the search for new resources, as well as for maximising the extraction of as much of the contained oil/gas as possible. Similar understanding is important for managing groundwater resources and for predicting how hazardous or radioactive waste or carbon dioxide will behave if stored or disposed of underground. Unravelling the complex behaviour of fluids as they flow through rock is difficult, but important. We cannot see through rock, so we need to predict how and where fluids flow. Understanding the type of rock, its porosity, the character and pattern of fractures within it and how fluids flows through it are important. Some contributors to this volume have been trying to understand real rocks in real situations and others have been working on computer models and laboratory simulations. Put together, these approaches have yielded very useful results, many of which are discussed in this volume.

Environmental Issues in the Geological Disposal of Carbon Dioxide and Radioactive Waste

A comparative assessment of the post environmental issues for the geological disposal of carbon dioxide (CO2) and radioactive waste (RW) is made in this chapter. Several criteria are used: the characteristics of RW and CO2; their potential environmental impacts; an assessment of the hazards arising from RW and CO2; and monitoring of their environmental impacts. There are several differences in the way that the long-term safety of the disposal of RW and CO2 is regulated and evaluated. While the regulatory procedures relating to the development of a facility for the disposal of RW in many countries with nuclear power programmes are well defined having evolved over several decades, those relating to CO2 disposal are less well developed. The results of this assessment show that, despite key differences, many of the approaches addressing environmental issues are similar. Additionally, much can be learned from the RW disposal experience which will be particularly relevant to the assessments of site performance for CO2 within a regulatory framework, particularly in the methods and approaches to long-term site performance assessment.

Unusual morphologies and the occurrence of pseudomorphs after ikaite (CaCO3·6H2O) in fast growing, hyperalkaline speleothems

Abstract Unusual speleothems, associated with hyperalkaline (pH > 12) groundwaters have formed within a shallow, abandoned railway tunnel at Peak Dale, Derbyshire, UK. The hyperalkaline groundwaters are produced by the leaching of a thin layer (<2 m) of old lime-kiln waste on the soil-bedrock surface above the tunnel by rainwater. This results in a different reaction and chemical process to that more commonly associated with the formation of calcium carbonate speleothems from Ca-HCO3-type groundwaters and degassing of CO2. Stalagmites within the Peak Dale tunnel have grown rapidly (averaging 33 mm y-1), following the closure of the tunnel 70 years ago. They have an unusual morphology comprising a central sub-horizontallylaminated column of micro- to nano-crystalline calcium carbonate encompassed by an outer sub-vertical assymetric ripple-laminated layer. The stalagmites are composed largely of secondary calcite forming pseudomorphs (<1 mm) that we believe to be predominantly after the ‘cold climate’ calcium carbonate polymorph, ikaite (calcium carbonate hexahydrate: CaCO3 · 6H2O), with minor volumes of small (<5 μm) pseudomorphs after vaterite. The tunnel has a near constant temperature of 8-9°C, which is slightly above the previously published crystallization temperatures for ikaite (<6°C). Analysis of a stalagmite actively growing at the time of sampling, and preserved immediately within a dry nitrogen cryogenic vessel, indicates that following crystallization of ikaite, decomposition to calcite occurs rapidly, if not instantaneously. We believe this is the first occurrence of this calcium carbonate polymorph observed within speleothems.

Gas generation and migration in deep geological radioactive waste repositories

Understanding the behaviour of gases in the context of radioactive waste disposal is a fundamental requirement in developing a safety case for the disposal of radioactive waste. Of particular importance are the long-term performance of bentonite buffers and cement-based backfill materials that may be used to encapsulate and surround the waste in a repository, and the behaviour of plastic clays, indurated mudrocks and crystalline formations that may be the host rocks for a repository. The EC Euratom programme funded project, FORGE, has provided new insights into the processes and mechanisms governing gas generation and migration with the aim of reducing uncertainty. This volume brings together papers on aspects of this topic arising from both the FORGE project and work undertaken elsewhere. This has been achieved by the acquisition of new experimental data coupled with modelling, through a series of laboratory and field-scale experiments performed at a number of underground research laboratories throughout Europe.

The Fate of Repository Gases (FORGE) project

Abstract Understanding the behaviour of gases in the context of radioactive waste disposal is a fundamental requirement and was the focus of the FORGE (Fate Of Repository GasEs) project. Of particular importance is the long-term performance of the bentonite buffers and the cement-based backfill materials that may be used to encapsulate and surround the waste in a repository for the geological disposal of radioactive waste and plastic clays, indurated mudrocks, and the crystalline formations that may be the host rocks of a repository. FORGE did not study salt host rocks or salt based backfill materials. FORGE has provided new insights into the processes and mechanisms governing gas generation and migration, with the aim of reducing uncertainty relating to the quantitative treatment of gas in performance assessment. This has been achieved by the acquisition of new experimental data coupled with modelling through a series of laboratory and field-scale experiments (performed at a number of underground research laboratories throughout Europe), and modelling. New methods were developed for upscaling from laboratory to field conditions, allowing the optimization of disposal concepts through detailed scenario analysis. Understanding a repository system to an adequate level of detail is required to demonstrate confidence in the assessment of site performance, recognizing that a robust treatment of uncertainty is desirable throughout this process.

Tectonic and climatic considerations for deep geological disposal of radioactive waste: A UK perspective.

Identifying and evaluating the factors that might impact on the long-term integrity of a deep Geological Disposal Facility (GDF) and its surrounding geological and surface environment is central to developing a safety case for underground disposal of radioactive waste. The geological environment should be relatively stable and its behaviour adequately predictable so that scientifically sound evaluations of the long-term radiological safety of a GDF can be made. In considering this, it is necessary to take into account natural processes that could affect a GDF or modify its geological environment up to 1millionyears into the future. Key processes considered in this paper include those which result from plate tectonics, such as seismicity and volcanism, as well as climate-related processes, such as erosion, uplift and the effects of glaciation. Understanding the inherent variability of process rates, critical thresholds and likely potential influence of unpredictable perturbations represent significant challenges to predicting the natural environment. From a plate-tectonic perspective, a one million year time frame represents a very short segment of geological time and is largely below the current resolution of observation of past processes. Similarly, predicting climate system evolution on such time-scales, particularly beyond 200ka AP is highly uncertain, relying on estimating the extremes within which climate and related processes may vary with reasonable confidence. The paper highlights some of the challenges facing a deep geological disposal program in the UK to review understanding of the natural changes that may affect siting and design of a GDF.

The Kayelekera uranium deposit, Northern Malawi: past exploration activities, economic geology and decay series disequilibrium

Abstract The present paper describes the exploration and evaluation work carried out by the Central Electricity Generating Board on the Kayelekera uranium deposit in Northern Malawi between 1983 and 1991. This is one of the largest Karoo age sandstone hosted uranium deposits yet discovered. Approximately 200 boreholes, ∼60% of which were fully cored, were drilled into the deposit during this evaluation. An important part of the ore reserve estimation undertaken by the Central Electricity Generating Board at Kayelekera was gaining an understanding of the uranium decay series distribution within the deposit. Being located in a near surface environment the deposit is subject to weathering effects caused by oxidising groundwater. Three ore types are recognised: reduced facies ore, oxidised facies ore and transitional facies ore containing both oxidised and reduced material in varying proportions. Being more mobile under oxidising conditions uranium tends to be leached from the oxidised parts of the deposit and re-deposited in more reducing parts. However its gamma emitting daughters tend to be less mobile in an oxidising environment leading to a marked disequilibrium between uranium and its daughters with the oxidised facies ore being depleted in uranium relative to its daughters and the reduced facies ore often showing relative enrichment.

Collation, management and dissemination of environmental research relating to urban areas in the UK. The approach used within the Natural Environment Research Council's URGENT Programme

The Urban Regeneration and the Environment Programme (URGENT) is a wide-ranging research programme concerned with the restoration and regeneration of urban conurbations in the UK. Its aim is to integrate urban ecological and environmental research across the geological, terrestrial, freshwater and atmospheric sciences. It is funded and managed by the UK Natural Environment Research Council (NERC) as one of their thematic programmes, but works in partnership with city authorities, industry and regulatory bodies. The URGENT programme has funded 40 projects in UK institutes and universities covering a wide variety of scientific research and is generating data, models and other information outputs across a broad spectrum. In anticipation of the creation of this valuable data resource and in response to the need to disseminate the results of the research as widely as possible, data management and quality assurance methods were implemented at the start of the programme. The evolution of the URGENT data management plan, its implementation within the research programme and the lessons learnt for the future are discussed.

Rare earth element placer deposits and alkaline volcanics: a case study from Aksu Diamas, Çanakli, Turkey

included detail on the igneous facies and simply have attempted to recognise weathered flow tops. Hitherto the Lower Basalt Formation was considered internally consistent despite having a geographical extent of over 3500 km and a variable thickness, which in areas has been recorded up to 531 m. The lack of robust and detailed stratigraphical information for the unexposed parts of the Antrim Plateau presents a significant hindrance to exploration that relies on information about the location and distribution of feeder systems (dykes, sills and plugs). In an attempt to address this lack of stratigraphic information we have undertaken detailed graphical logging of two cores from the Carnduff area, a field section from Browns Bay, Island Magee, as well as comprehensive petrographical analysis. The study focuses on the lowermost 160 m of the basalts from which it is clear that there are complex internal variations. The basalts were formed by a series of tabular and compound flows most of which can be correlated laterally across the area. By identifying and characterising the geometry and morphologies of these flows, it is possible to break the Lower Basalt Formation down into three smaller lower and upper units consisting of tabular basaltic lava flows and the middle unit of much smaller compound flows. Ultimately, the aim is to generate a robust stratigraphic model for the Lower Basalt Formation that can be applied elsewhere on the plateau to correlate key flows at the base of the Antrim Lava Group. By mapping these flows across the area it may be possible to locate mineralogical important feeder dyke systems.

Timing and source of rare earth element mineralisation in the Ditrău alkaline complex, Romania

complex, Romania Richard Shaw , Kathryn Goodenough, Nick Roberts, Victoria Honour, Matt Horstwood and Christoph Lenz British Geological Survey, Environmental Science Centre, Nottingham, United Kingdom; British Geological Survey, Lyell Centre, Edinburgh, United Kingdom; NERC Isotope Geosciences Laboratory, Nottingham, United Kingdom; University of Cambridge, Cambridge, United Kingdom; Institut für Mineralogie und Kristallographie, Faculty of Geosciences, Geography and Astronomy, University of Vienna, Austria