Sandstone-type uranium deposits are among the most economic sources of uranium. Despite their significance, the tabular deposits on the Colorado Plateau and roll-front deposits in Nebraska have not been studied adequately. There are important differences between the tabular Colorado Plateau and Nebraska roll-front deposits, including their ore mineralogy, distribution and habit of ore-bodies, alteration, and mechanisms of ore deposition. The U-Pb ages of uranium minerals from the Colorado deposits indicate four stages of mineralization, spanning from the early Oligocene to late Pliocene. Uranium and V minerals include coffinite, montroseite and carnotite and are associated with both biogenic and non-biogenically precipitated sulphides. Two generations of coffinite mineralization from the Three Crow roll-front deposit in Nebraska were identified. This mineralization precipitated during the early Pliocene and late Miocene. The U-Th activity ratios of U minerals suggest a net accumulation of uranium within the limbs of the roll-front. Evolving oxidation fronts are implied by multiple sulphide generations as indicated by their delta 34S compositions.

Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisor: A. Daniel Hill. Vita. Includes bibliographical references. Also available from UMI.

No description available.

No description available.

Large-scale sandstone injectite complexes located in California and in Tunisia have exposures of external geometries and sedimentary structures.  Substantial macroscale erosion occurred along the margins between the injected sandstones and host mudstones that include scalloped upper margins that cut up to 5 m into the overlying host mudstones. Sedimentary structures preserved in the sandstone injectite complexes record fluid-flow, sedimentation and post-sedimentation processes.  Bedload layers moving in traction along fluid-sediment interfaces is identified as a significant transport mechanism of grains in sills, low-angle dykes, and irregular injectites, as evidenced by laminae defined by differences grain size, grain composition, and grain packing.  High-angle sandstone dykes are characterised by a distinct suite of sedimentary structures that include horizontal bands and pipes.  Horizontal bands record the movement of fluidised sand as bands during the waning phase of sand injection.  Pipes are interpreted to have formed due to post-sand-injection consolidation and fluid-escape.  The distinct sedimentary structures and microtextures that characterise each intrusive element reflect the coupled relationships between the fluid-flow and sedimentation processes and the element type. Sedimentation, post-sedimentation, and diagenetic processes thereafter, resulted in the formation of heterogeneous permeabilities; values vary three-orders-of-magnitude.  The heterogeneity is predictable and correlates with the type of intrusive element and its primary and secondary microfabrics.  This link demonstrates the influence of primary sedimentation processes and secondary diagenetic processes on the injected sandstone permeability.  By constraining the permeability heterogeneity of injected sandstones, it is possible to accurately quantify and thereby anticipate their impact on fluid flow in sedimentary basins.

Master of Science / Department of Geology / Allen W. Archer / Hydrocarbon production throughout the continental United States has declined in past decades. New interpretations together with advanced recovery techniques can increase production in older fields. Re-examining these types of underdeveloped resources is a simple and cost effective tool that can be readily used to increase hydrocarbon production throughout the mid-continent. Pennsylvanian sandstones throughout Oklahoma and Kansas are known for their excellent reservoir qualities. The focus of this study is the upper Pennsylvanian Tonkawa Formation, a sandstone dominated unit. The Tonkawa has been informally correlated to both the Stalnaker and Tonganoxie sandstones in Kansas. Previous publications do not present a unified understanding of the depositional environments that are seen across state borders. The interpretations vary from fluvio-deltaic to marine environments. A cohesive interpretation is necessary to understand paleo-processes and efficiently exploit the reservoir for hydrocarbons. The study presents a regional analysis covering an eleven county area in northwest Oklahoma. Analysis of core and well log data is used to determine the range of depositional environments of the Tonkawa sandstone. Sedimentary structures, mineral assemblages, and lithologies of selected cores are described and correlated with well log data. With this data, structural isopach maps are constructed using Petra software. Earlier interpretations have relied primarily on well log data, focusing on core data rather than geophysical logs, allowing for a more detailed and accurate interpretation. Analysis of transitional sedimentary sequences, such as the Tonkawa, can be applied to sandstones deposited in similar environments throughout the mid-continent.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science. October 1990 / Problems arising from a disparity in viewpoints regarding the surface form of the Tsondab Sandstone Formation, central Namib desert, Namibia, are examined through literature review and field investigation. It is shown that large distal low-angle fans, proposed in what has been termed the Low-Angle Fan model, are absent or limited to proximal reaches of the study area. The depositional sequence identified in what has been termed the Axial Deposition Model along the Kuiseb River in the northern part of the study area is safely applicable to the rest of the study area. Further, new deposits of the Tsondab Sandstone Formation are identified. The problem of the age of the Namib desert in its fossil and active forms is discussed. The processing of satellite images is used and is shown not to be a viable technique for the identification of sedimentary bodies which are partly mantled by deposits of sediments of a similar nature. / MT2017

Clays which exist in formations in the vicinity of injection and disposal wells is a worldwide problem in the petroleum industry. Clays can be categorized as two major groups: swelling clays, which include smectite group clays, and dispersing clays, which include the kaolinite groups of clays. Therefore, two basic damage mechanisms of clay minerals are swelling and dispersion. Both mechanisms cause pore plugging, and thus aggravate hydrocarbon ease of flow. In this thesis, the effect of temperature, injected water chemical composition, pH, and flowrate of the injected fluid were tested experimentally. Clay mineralogy, chemistry, and composition of the exchangeable cations were also examined. The existing theoretical models of evaluation of forces between clay particles and the rock matrix were used to quantify the interactions. Coreflood experiments were conducted to determine the effect of parameters such as variation of temperature, flowrate, pH, presence of various salts in working solution and their concentration. The results obtained from experimental and theoretical work show that clay minerals in sandstone formation are subject to fines migration and can cause a detrimental impact on the reservoir permeability. Every aforementioned factor has its influence on clays behavior and therefore, a degree of fines migration. The work accomplished summarizes and concludes what parameters sensitize clays migration. Moreover, recommendations for formation damage due to fines migration are given. The scope of work presented can be useful for petroleum engineers as well as geologists and clay mineralogists.

Thesis (M.S.)--West Virginia University, 2004. / Title from document title page. Document formatted into pages; contains ix, 135 p. : ill. (some col.), maps. Includes abstract. Includes bibliographical references (p. 93-95).

The objective of this research was to determine the impact of algal colonisation on natural stone masonry. Experimental work was carried out to determine the physical and chemical damage caused by micro-algae using reflected light microscopy, Scanning Electron Microscopy and Inductively Coupled Plasma - Atomic Emission Spectroscopy. Colonisation experiments were performed on individual mineral chips of quartz, calcite, dolomite, siderite, labradorite, orthoclase, a perthitic albite, muscovite and montmorillonite; as well as the Giffnock sandstone, a traditional building stone of the Glasgow area. Work was also carried out to determine the effect of algal colonisation on the absorption of water into a masonry surface. The research determined that algae create an alkaline environment in the areas they colonise. Algal mediated damage to the mineral substrates includes the dissolution and pitting of carbonate surfaces as well as the etching of plagioclase feldspar surfaces. Algal colonisation preferences were noted throughout the experiment with algae preferentially colonising kinks and steps in the topography of mineral surfaces as well as grain edges. Preferences were also seen in the colonisation of the Giffnock sandstone with micas showing heavy colonisation compared to other minerals in the lithology. Algal swelling and contraction cycles were examined in Environmental Scanning Electron Microscopy experiments and the impact that this physical swelling may have on the stone is modelled. Algal biofilms at the surface of the stone lead to an acceleration in the rate at which water enters the surface of the stone, this is important as water is the main weathering catalyst for masonry weathering. The findings of this project implicate algae in the weathering of natural stone masonry through enhanced mineral dissolution, mineral etching and pitting, patina formation, physical weathering through swelling cycles and the alteration of the surface physical properties in relation to water absorption.