Formation of hexagonal boron nitride (h-BN) by carbothermic reduction of B2O3 under nitrogen atmosphere at 1500oC was investigated. Reaction products were subjected to powder X-ray diffraction analysis, chemical analysis and were examined by SEM. B4C was found to exist in the reaction products of the experiments in which h-BN formation was not complete. One of the aims of this study was to investigate the role of B4C in the carbothermic production of h-BN. For this purpose, conversion reaction of B4C into h-BN was studied. B4C used in these experiments was produced in the same conditions that h-BN was formed, but under argon atmosphere. It was found that formation of h-BN from B4C&ndash / B2O3 mixtures was slower than activated C&ndash / B2O3 mixtures. It was concluded that B4C is not a necessary intermediate product in the carbothermic production of h-BN. Some additives are known to catalytically affect the h-BN formation. The second aim of this study was to examine the catalytic effect of some alkaline earth metal oxides and carbonates, some transition metal oxides and cupric nitrate. It was found that addition of 10wt% CaCO3 into the B2O3+C mixture was optimum for increasing the rate and yield of h-BN formation and decreasing the B4C amount in the products and that the reaction was complete in 2 hours. CaCO3 was observed to be effective in increasing the rate and grain size of the formed h-BN. Addition of cupric nitrate together with CaCO3 provided a further increase in the size of the h-BN grains.

The Savannah River Site (SRS) deposits in the Southeastern US between 30-45 m of depth are calcium carbonate-rich, marine-skeletal, Eocene-aged sediments with varying clastic content and extensive diagenetic alteration, including meter-sized caves that coexist with brittle and hard limestone. An experimental investigation including geotechnical (P- and S-wave velocities, tensile strength, porosity) and geochemical (EDS, XRD, SEM, N2-adsorption, stable isotopes, K-Ar age dating, ICP-assisted solubility, groundwater) studies highlighted the contrast between hard and brittle limestones, their relationship with cave formation, and allowed calculation of parameters for geochemical modeling. Results demonstrate that brittle and hard limestones bear distinct geochemical signatures whereby the latter exhibits higher crystallinity, lower clastic load, and freshwater-influenced composition. Results also reveal carbonate diagenesis pathways likely driven by geologic-time seawater/freshwater cycles, microorganism-driven micritization, and freshwater micrite lithification. The second section of this investigation dealt with SRS surface soils which are largely coarse-grained and rich in iron oxides with various degrees of maturity. These soils were simulated in the laboratory using Ottawa sands that were chemically coated with goethite and hematite. Surface (SEM, AFM, N2-adsorption) and geotechnical properties (fabric, small-strain stiffness, shear strength) were investigated on the resulting "soil analog". Results indicate that iron-oxide coated sands bear distinct inherent fabric and enhanced small-strain stiffness and critical state parameters when compared to uncoated sands. Contact mechanics analyses suggest that iron oxide coatings yield an increased number of grain-to-grain contacts, higher surface roughness, and interlocking, which are believed to be responsible for the observed properties.

The flux of CO2 between the ocean and the atmosphere is an important measure in determining local, global, and regional, as well as short term and long term carbon budgets. In this study, air-sea CO2 fluxes measured using a floating chamber were used to examine the spatial and temporal variability of CO2 fluxes in Florida Bay. Measurements of dissolved inorganic carbon and total alkalinity obtained concurrently with chamber measurements of CO2 flux allowed calculation of ΔpCO2 from flux measurements obtained at zero wind velocity. Floating chamber measurements of ΔpCO2 were subsequently coupled with wind speed data to provide a simple yet reliable means of predicting absolute flux values. Florida Bay is a marine-dominated, sub-tropical estuary located at the southern tip of the Florida peninsula. Spatial variability within the bay reveals four distinct regions that appear to be affected by a variety of physical, chemical and biological processes. In the eastern part of the bay, the waters tend to be oversaturated with respect to CO2, likely due to the input of freshwater from Taylor Slough. The central portion of the bay is characterized by a number of extremely shallow semi-isolated basins with limited exchange with the rest of the bay. This area is typically undersaturated with respect to CO2 and provides a sink for atmospheric CO2. Both the northern and southern regions were highly variable both spatially and temporally.

Alkaline/surfactant/polymer (ASP) flooding is of increasing interest and importance because of high oil prices and the need to increase oil production. The benefits of combining alkali with surfactant are well established. The alkali has very important benefits such as lowering interfacial tension and reducing adsorption of anionic surfactants that decrease costs and make ASP a very attractive enhanced oil recovery method provided the consumption is not too large and the alkali can be propagated at the same rate as a synthetic surfactant and polymer. However, the process is complex so it is important that new candidates for ASP be selected taking into account the numerous chemical reactions that occur in the reservoir. The reaction of acid and alkali to generate soap and its subsequent effect on phase behavior is the most crucial for crude oils containing naphthenic acids. Using numerical models, the process can be designed and optimized to ensure the proper propagation of alkali and effective soap and surfactant concentrations to promote low interfacial tension and a favorable salinity gradient. The first step in this investigation was to determine what geochemical reactions have the most impact on ASP flooding under different reservoir conditions and to quantify the consumption of alkali by different mechanisms. We describe the ASP module of UTCHEM simulator with particular attention to phase behavior and the effect of soap on optimum salinity and solubilization ratio. Several phase behavior measurements for a variety of surfactant formulations and crude oils were successfully modeled. The phase behavior results for sodium carbonate, blends of surfactants with an acidic crude oil followed the conventional Winsor phase transition with significant three-phase regions even at low surfactant concentrations. The solubilization data at different oil concentrations were successfully modeled using Hand's rule. Optimum salinity and solubilization ratio were correlated with soap mole fractions using mixing rules. New ASP corefloods were successfully modeled taking into account the aqueous reactions, alkali/rock interactions, and the phase behavior of soap and surfactant. These corefloods were performed in different sandstone cores with several chemical formulations, crude oils with a wide range of acid numbers, brine with a wide range of salinities, and a wide range of temperatures. 2D and 3D sector model ASP simulations were performed based on field data and design parameters obtained from coreflood history matches. The phenomena modeled included aqueous phase chemical reactions of the alkaline agent and consequent consumption of alkali, the in-situ generation of surfactant by reaction with the acid in the crude, surfactant/soap phase behavior, reduction of surfactant adsorption at high pH, cation exchange with clay, and the effect of co-solvent on phase behavior. Sensitivity simulations on chemical design parameters such as mass of surfactant and uncertain reservoir parameters such as kv/kh ratio were performed to provide insight as the importance of each of these variables in chemical oil recovery. Simulations with different permeability realizations provided the range for chemical oil recoveries. This study showed that it is very important to model both surface active components and their effect on phase behavior when doing mechanistic ASP simulations. The reactions between the alkali and the minerals in the formation depend very much on which alkali is used, the minerals in the formation, and the temperature. This research helped us increase our understanding on the process of ASP flooding. In general, these mechanistic simulations gave insights into the propagation of alkali, soap, and surfactant in the core and aid in future coreflood and field scale ASP designs. / text

An appreciation of the extent of syndepositional fracturing, faulting, and cementation of carbonate platform margins is essential to understanding the role of early diagenesis and compaction in margin deformation. This study uses integrated lidar and outcrop data along the Capitan Reef from an area encompassing the mouths of both Rattlesnake and Walnut Canyons. Mapping geomorphic expressions of syndepositional faults and fractures at multiple scales of observation was the main approach to delineating zones of syndepositional fractures. Ridge- groove couplets visible in exposures of the Capitan Reef throughout the Guadalupe Mountains were targeted because the ability to identify these as signs of syndepositional fracture development would have implications for the entire reef complex. Results show that these ridgegroove couplets are the product of differential weathering of syndepositional as well as burial-related fractures. Recessive grooves have an average syndepositional fracture spacing of ~13 m whereas ridges have a spacing of ~33 m. vi Smaller (~5-20 m-wide) scale erosional lineaments common in the study area and mappable on airborne lidar are formed by differential erosion of planes of syndepositional faults. Maps of these fault lineaments on the lidar show that syndepositional faults extend laterally for 300 m - 2000 m and relay near the terminations of the faults at each end. Faults can be further grouped into fault systems consisting of sets of faults connected by fault relays that extend for at least the entire length (~12 km) of the study area. Although vertical displacement along faults is typically less than 11 m, syndepositional faults result in changes in structural dip domain of 1-6 degrees across an individual fault. Even smaller erosional lineaments (10 cm-1 m) are visible on the airborne lidar that form as a result of differential erosion of individual fractures. Larger fractures (> 20 cm) can be reliably mapped on the lidar, but smaller features (< 20 cm) cannot be reliably mapped with currently available data and can only be captured using field studies. Fracture fill types are heterogeneous along strike as shown by comparisons of field study locations. Siliciclastic-dominated fills are likely sourced from overlying siliciclastic units of the shelf, which, in this area, were from the Ocotillo Siltstone. These silt-filled fractures are broadly distributed, indicating preferential development and infill of syndepositional fractures during the deposition of the Ocotillo Siltstone in the G27/28 high-frequency sequences. Development of early fractures is also shown to have been influenced by mechanical stratigraphy with changes in fracture spacing between massive to thick-bedded shelf-margin (~17 m fracture spacing) and outer-shelf facies tracts versus thin-bedded outer-shelf and shelf-crest (~28 m fracture spacing). Ultimately, this study demonstrated that the Capitan shelf margin was ubiquitously overprinted by syndepositional fracturing and faulting and that this nearsurface structural modification influenced early diagenetic patterns and internal vii sedimentation throughout the reef margin. Before this study, the extent and nature of syndepositional fracture/fault development within the margin were largely unquantified. Here, by integrating field observations and surface weathering reflections of these fractures as observed in the lidar, we can demonstrate a widespread impact of early fracturing more akin to analogous early-lithified margins such as the Devonian of the Canning Basin of Australia. / text

Recently, oil prices and oil demand are rising and are projected to continue to rise over the long term. These trends create great potential for enhanced oil recovery methods that could improve the recovery efficiency of reservoirs all over the world. The greatest challenges for enhanced oil recovery involve the technical uncertainty with design and performance, and the high financial risk. Pilot tests can help mitigate the risk associated with such projects; however, there is a question about the value of information from the tests. Decision support can provide information about the value of an enhanced oil recovery project, which can assist with alleviating financial risk and create more potential opportunities for the technology. The first objective of this study is to create a new simplified method for modeling oil production histories of enhanced oil recovery methods. The method is designed to satisfy three criteria: 1) it allows for quick simulations based on only a few physically meaningful input parameters; 2) it can create almost any potential type of realistic production history that may be realized during a project; and 3) it applies to all nonthermal enhanced oil recovery methods, including surfactant-polymer, alkali-surfactant polymer, and CO₂ floods. The developed method is capable of creating realistic curves with only four unique parameters. The second objective is to evaluate the predictive method against data from pilot and field scale projects. The evaluations demonstrate that the method can fit most realistic production histories as well as provided ranges for the input parameters. A sensitivity analysis is also performed to assist with determining how all of the parameters involved with the predictive method and the economic model influence the forecasted value for a project. The analysis suggests that the price of oil, change in oil saturation, and the size of the reservoir are the most influential parameters. The final objective is to establish a method for a decision analysis that determines the value of information of a pilot for enhanced oil recovery. The analysis uses the predictive method and economic model for determining economic utilities for every potential outcome. It uses a decision-based method to ensure that the non-informative prior probability distributions have an unbiased, consistent, and rational starting point. A simple example demonstrating the process is discussed and it is used to show that a pilot test provides some valuable information when there is minimal prior information. For future work it is recommended that more evaluations are performed, the decision analysis is expanded to include more input parameters, and a rational and logical method is developed for determining likelihood functions from existing information. / text

Manito Lake is a large, perennial, Na-SO4 dominated hypersaline lake located in the northern Great Plains of western Canada. Significant water level decrease over the past several decades has lead to reduction in volume and surface area. Today, the lake is 15% of its mid -20th century volume and 46% of its former area. This decrease in water level has exposed large areas of nearshore microbialites. These organosedimentary structures have various external morphologies, vary in mineralogical composition, and show a variety of internal fabrics from finely laminated to massive and clotted. These features range from small, mm-scale, finely laminated encrustations to large, reef-like structures up to 5 m high and over 500 m long. Although there is relatively little consistent lateral variability in terms of morphology, the structures do vary significantly with elevation in the basin. Petrographic evidence confirms a strong biological involvement in the formation of these structures. Nonetheless, inorganic and trapping mechanisms may also play a role. Dolomite, aragonite, and calcite are the most commonly found minerals in these structures, however, monohydrocalcite, magnesian calcite, hydromagnesite, dypingite, and nesquehonite are also present. The calcite is a pseudomorph after ikaite, which forms an open porous dendritic and shrub-like fabric, comprising the interiors of massive shoreline microbialite mounds and pinnacles. These ikaite pseudomorphs are encased in millimeter to centimeter-scale laminated dolomite-aragonite rinds. Radiocarbon dating and stable isotope analysis have indicated microbialite formation began about 2200 yBP in a shallow, productive, saline and cold lake. Over the next 900 years, the microbialites record a transgressing lake in a cool climate, which corresponds to a period not previously documented in this region but is referred to as the Dark Ages Cold Period, which has been documented in other parts of the Northern Hemisphere. This is followed by 500 years of warmer conditions coinciding with the Medieval Climate Anomaly. Starting about 600 years ago the lake experienced a dramatic decrease in level resulting in formation of extensive carbonate pavements, cemented siliciclastics, rinds, and coatings.

Un certain nombre de réactions de décomposition des solides de la forme : S1 &#8594 S2 + &#124G&#124 présentent un grand intérêt pratique. On peut citer la préparation des liants hydrauliques obtenus par déshydratation des hydrates salins. Ces réactions constituent aussi un procédé courant d'obtention de catalyseurs de synthèse pour la chimie industrielle : Les oxydes métalliques en particulier peuvent être obtenus par cette voie à partir des sels du métal (carbonates - hydroxydes - formiates, etc, ...). Malgré l'intérêt pratique de ces réactions leur mécanisme est souvent mal connu. L'hétérogénéité du système est responsable de cette méconnaissance car elle rend délicate les mesures dans la zone réactionnelle et ne permet pas toujours de maîtriser l'ensemble des paramètres qui influent sur la réaction. La plupart des études fondamentales consacrées aux réactions de ce type ont pour but de décrire l'évolution géométrique de l'interface réactionnel ou d'interpréter par des lois formelles les courbes d'évolution en fonction du temps. Nous avons cherché dans ce mémoire à progresser dans le sens d'une meilleure connaissance des processus chimiques qui affectent les réactions de décomposition des solides.

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