Thesis (doctor of philosophy)--Göteborg University, 2006. / Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisors: Earle F. McBride and Kitty L. Milliken. Vita. Includes bibliographical references. Also available from UMI.

Thesis (Ph. D.)--University of Texas at Austin, 2004. / Includes bibliographical references (p. 278-297). Available also in an electronic version.

No description available.

An understanding of groundwater flow is essential in many aspects of mining. This is especially true for the sandstones of the Manitou Falls Formation, which overlie uranium deposits in the Athabasca Basin of northern Saskatchewan. Experience has shown that the hydraulic conductivities of these sandstones can be relatively high, especially in zones containing natural fractures, thus leading to potentially problematic groundwater inflow rates. This thesis presents the results of a study of hydraulic conductivity of the Manitou Falls Formation, in which detailed core logging and laboratory testing were undertaken for samples from two boreholes at the McArthur River mine site. Results from the logging and laboratory testing were interpreted in context provided by multiple packer tests conducted in these boreholes. Through core logging, indicators of conductive zones were identified. These indicators include fracture orientation (sub-vertical fractures were found to have more of an impact on conductivity than horizontal fractures), infilling, and staining. The laboratory testing program involved the measurement of hydraulic conductivities of fractured core samples across a span of effective confining pressures representative of in-situ conditions. Changes in fracture aperture were simultaneously recorded at each confining pressure level. It was found that theoretical relationships between aperture change and fracture conductivity represent the observed behavior of the samples reasonably well when fracture roughness is accounted for. The laboratory testing also confirmed the effects of fracture staining and infilling on hydraulic conductivity inferred from core logging and packer testing results. The results provide insights into the mechanisms underlying flow in fractured intervals of the Manitou Falls Formation, and provide guidance for selecting intervals to investigate during future packer testing in this formation.

Development of Middle Triassic red-bed plays is commonly hampered by a lack of understanding of the stratigraphic relationships between reservoir sandstones. This inadequacy reflects poor palynological recoveries and a general deficiency in understanding the controls on palynological preservation. The sedimentology and palynology of Triassic red-bed facies, from the UK North Sea and onshore analogues, are studied to determine the sedimentary controls on palynological preservation and to investigate whether palynology is useful in these facies, where other stratigraphic techniques do not always provide unique solutions. The Skagerrak Formation (Quadrants 22, 29 and 30) typically comprises ephemeral channel and sheet-flood deposits in the north, but includes sediments deposited in perennially wet, alluvial plain and lacustrine settings in the south. Further north (Quadrant 210), the Cormorant Formation comprises dry alluvial deposits. Onshore, the Bromsgrove Sandstone Formation is characterised by ephemeral channel deposits that pass progressively upwards into tidally-influenced, fluvial and estuarine deposits; these are partly comparable with sediments in the Tarporley Siltstone Formation. Palynological analysis reveals that, in the absence of palynomorphs, palynodebris and absolute organic concentration can distinguish between preservational regimes, and thus environment. Palynological preservation demonstrates a correlation with facies deposited in perennially wet, alluvial plain, lacustrine and tidally influenced settings. Organic assemblages distinguish between members in the Bromsgrove Sandstone Formation, and can subdivide members on palaeoenvironmental criteria, which is of local value in correlation. Palynological assemblages are mostly lacking where ephemeral depositional processes were dominant. The assemblages demonstrate a close relationship with sedimentary facies, their associations, and sediment colour, but the oxidation potential of pore fluids, during and soon after deposition, is an overriding control on organic preservation. These relationships are all beneficial for targeting sediments for further palynological analysis.

This thesis investigates the origin of large-scale sandstone intrusions.  A new approach combining seismic, well data, core and outcrop observations with numerical modelling has been undertaken. Two possible end members of saucer-shaped, seismic-scale sandstone intrusions from the North Sea were identified on the basis of seismic data and core observation.  Diagnostic criteria were proposed to differentiate between fully and only partially injected sand bodies.  Outcrop and core data presented in this thesis provide a direct example and analogue for seismic and sub-seismic scale sandstone intrusions, highlighting the brittle nature of the host rock deformation at all levels within the examined intrusion complexes.  On this basis, the rheological behaviour of the host strata at the time of sand injection is inferred to be elastic with brittle fracturing.  This outcome is used as an input condition for Finite Difference and Finite Element modelling that aim to test hypotheses describing triggering mechanisms and estimate their regional extent, depth and overpressures present during sand injection.  The results of numerical modelling indicate that formation of the North Sea sandstone intrusions could potentially be triggered by catastrophic event(s) such as a meteorite impact or earthquakes, leading to sand liquefaction and remobilization.  It has also been shown that depths at which sand injection can take place reach 1 km.  Only supra-lithostatic pressures generate bodies composed of lower, bedding concordant part of intruded or depositional origin feeding inclined dykes at its marginal parts resembling those observed today on seismic data from the North Sea and in outcrops.

Hitherto the bivalve fauna of the Spilsby Sandstone and contiguous deposits including the lower part of the Sandringham Sands and Speeton Clay of-Middle Volgian to Ryazanian age has been inadequately described. As a consequence of this study 92 taxa have been recorded. 45 of these are described fully and include 13 new species and one new subgenus. Information has been obtained from the author's collecting and from museum' collections. Locality and section information is given for sites examined by the author. The preservation of the fauna is normally as moulds, but cold cure silicone rubber has been used to obtain casts with great success. The ecology of the less well understood bivalves is discussed. Five bivalve dominated assemblages are recognised. They represent various shallow marine facies. The sediments include glauconitic sands and silts with condensed sequences containing phosphatised nodules and also a sideritic ironstone occurs. A facies model is produced for the East Midlands Shelf, and the contemporary relationships with other parts of England are discussed. The Spilsby basin represents a westerly embayment or estuary of the Southern North Sea basin. In Middle Volgian times there were marine connections to the Wessex basin to the south, but with the subsequent draining of this latter area in Upper Volgian to Ryazanian times to restricted marine, brackish and freshwater lagoonal environments, open marine connection ceased. The Spilsby basin remained fully marine during these times, but became more enclosed. The Spilsby bivalve fauna indicates strong faunal similarities with Boreal regions, and in particular with East Greenland and the Russian Platform. The fauna also compares closely with the sandy Upper Kimmeridgian facies in central England but contrasts strongly with the contemporary faunas of the Portland and Purbeck Beds. The relationships of the Spilsby fauna with other Boreal regions and with Tethyan Europe are discussed.

Present models suggest that fluvial and marine depositional patterns were distinct from modern patterns prior to the appearance of land plants. Although these models are likely correct, problems exist when one attempts to distinguish between fluvial and shallow marine deposits in pre-Silurian strata, making it difficult to accurately determine depositional patterns. The lack of land plants and scarcity of body and trace fossils, especially in Precambrian and early Cambrian strata, make identification difficult. Based on core data and limited outcrops, the Lower Hickory Sandstone, a late Cambrian sandstone, has been interpreted to progress from fluvial to shallow marine. These data have allowed the development of an overall depositional model, but minimal detail of facies changes is available. Based on the limited data, both deltaic and estuarine models have been suggested for the Lower Hickory. Mining of the Lower Hickory for frac sand has created highwalls in the CarmeuseNA Mine, which provides an opportunity to study facies changes at this site. The CarmeuseNA Mine, located in McCulloch County, Texas, has exposed the formation along ~500 m long and 20 m-high faces, respectively. Because of limited exposure, only the south and west walls, as well as part of the east wall, could be examined. Digital photographs of the faces were mosaiced using standard photogrammetrical practices to produce visual representation of the highwalls. Bedding geometry was then mapped on the digital images to facilitate a detailed interpretation of the depositional process. Core and well data were used to map Hickory thickness to produce an isopach map. Four primary facies were observed in the quarry, dominated by small-scale and large-scale cross-bedding. Paleocurrents are generally unidirectional to the southsoutheast indicating a braided fluvial origin, but rarely opposing directions are seen. Bioturbation is rare low in the section, but increases upwards. Together with the rare herringbone cross-bedding, clay drapes, and bioturbation, a tidal influence is strongly suggested. The model suggested is a braided stream setting influenced and reworked by tides. A braided-delta fed by braided streams guided by a ridge and swale-dominated setting, which served as the sediment supply for the delta, is proposed.

Knowledge of reservoir porosity, permeability, and capillary pressure is essential to exploration and production of hydrocarbons. Although porosity can be interpreted fairly accurately from well logs, permeability and capillary pressure must be measured from core. Estimating permeability and capillary pressure from well logs would be valuable where cores are unavailable. This study is to correlate permeability with porosity to predict permeability and capillary pressures. Relationships between permeability to porosity can be complicated by diagenetic processes like compaction, cementation, dissolution, and occurrence of clay minerals. These diagenetic alterations can reduce total porosity, and more importantly, reduce effective porosity available for fluid flow. To better predict permeability, effective porosity needs to be estimated. A general equation is proposed to estimate effective porosity. Permeability is predicted from effective porosity by empirical and theoretical equations. A new capillary pressure model is proposed. It is based on previous study, and largely empirical. It is tested with over 200 samples covering a wide range of lithology (clean sandstone, shaly sandstone, and carbonates dominated by intergranular pores). Parameters in this model include: interfacial tension, contact angle, shape factor, porosity, permeability, irreducible water saturation, and displacement pressure. These parameters can be measured from routine core analysis, estimated from well log, and assumed. An empirical equation is proposed to calculate displacement pressure from porosity and permeability. The new capillary-pressure model is applied to evaluate sealing capacity of seals, calculate transition zone thickness and saturation above free water level in reservoirs. Good results are achieved through integration of well log data, production data, core, and geological concepts.