Occurrences of carbonate-cemented nodules and concretions exposed on the seafloor that contain cements with light carbon isotopes, indicating a contribution of methane-derived carbon, are commonly interpreted to be indicators of seafloor fluid venting. Thus, their presence is commonly used as an indicator of the possible occurrence of methane gas hydrate within the near subsurface. While some of these carbonates exhibit facies that require formation on the seafloor, the dominant fine-grained lithology associated with these carbonates indicates they were formed as sedimenthosted nodules within the subsurface and are similar to nodules that are obtained from the subsurface in Deep Sea Drilling Project, Ocean Drilling Project, and Integrated Ocean Drilling Project boreholes. Here we present the hypothesis that the occurrence of these carbonates on the seafloor may instead indicate areas of persistent seafloor erosion.

Mineralogical and isotopic analysis of authigenic carbonates from different gas hydrate-bearing seepage structures in the Derugin Basin (Sea of Okhotsk) are presented. The analysis showed the existence of four morphological types of carbonates, with all of them mainly of Mg-calcite.13C values of carbonates generally light owing to the inheritance of carbon from microbial methane. 13C-enriched samples at the VNIIOkeangeologia structure with 13C values of up to +9.3‰ represent carbonate precipitation due to methanogenesis. The calculated equilibrium 18O values of carbonates in general correspond to measured values.

L'objectif de cette thèse est de reconstituer l'évolution de la plate-forme carbonatée de Kruja, appartenant à la marge passive d'Apulie en Albanie, du Crétacé à l'Éocène. Les propositions sont: (1) L'établissement d'un nouveau cadre stratigraphique du Crétacé inférieur (terminal) et du Crétacé supérieur (avec 7 biozones, de CsB1 à CsB7), ainsi qu'une meilleure définition lithologique du Paléocène et de l'Éocène; (2) Des précisions sur la durée des lacunes liées aux émersions à la fin du Crétacé supérieur et pendant l'Éocène inférieur, et la découverte de nouvelles lacunes (de 16 à 60 Ma), liées essentiellement à l'activité de failles synsédimentaires; (3) La détermination d'une émersion, non reconnue jusqu'ici, au passage des biozones CsB5-CsB6, en s'appuyant sur des données de géochimie nouvelles (Sr, δ¹³C et δ¹⁸O); (4) La caractérisation de la série carbonatée par un ensemble de vingt-six nouveaux faciès, témoins de paléoenvironnements qui s'étendent des zones littorales (plate-formes interne et externe) jusqu'au bassin; (5) La mise en évidence de l'importance de la diagenèse des calcaires (dolomitisation et recristallisation), grâce à l'analyse pétrographique, du Sr, du δ¹⁸O , de la covariance des valeurs δ¹³C et δ¹⁸O et de la distribution des REE; (6) La distinction, dans cette plate-forme, entre: (a) une Partie orientale qui se caractérise par une sédimentation de plate-forme interne durant le Crétacé supérieur et le Paléocène et une sédimentation de plate-forme externe durant l'Éocène moyen à supérieur; ces deux types de sédimentation étant séparés par des lacunes stratigraphiques, témoins parfois d'épisodes d'émersion, avec érosion et sédimentation (bauxites) continentales; et (b) une Partie occidentale qui se caractérise par une sédimentation de plate-forme interne, reconnue localement depuis l'Albien jusqu'au Maastrichtien inférieur, et une sédimentation différenciée (plateforme externe et bassin) à partir du Maastrichtien supérieur (CsB7) jusqu'à l'Éocène moyen à supérieur. Ces régimes de sédimentation sont interrompus par des lacunes stratigraphiques majeures liées aux failles synsédimentaires, de décrochement; (7) L'établissement d'un modèle d'évolution de la plate-forme de Kruja, avec: (a) une période de stabilité qui s'étend de l'Albien au Santonien inférieur, caractérisée par une sédimentation de plate-forme interne, et montrant une évolution de type bahamien; (b) une période d'instabilité tectonique entre le Santonien supérieur et l'Éocène moyen à supérieur, avec deux phases d'érosion (de 16 et 17 Ma); (8) L'hypothèse de la présence d'une zone de transition (flexure continentale ?) entre les deux parties de la plate-forme de Kruja. La comparaison entre la plate-forme de Kruja en Albanie et celle de Gavrovo en Grèce semble bien témoigner d'une histoire paléogéographique commune, dans l'évolution globale de la marge passive d'Apulie, appartenant aux Alpes Hellénides. ______________________________________________________________________________ MOTS-CLÉS DE L’AUTEUR : Plate-forme carbonatée, Biostratigraphie, Faciès, Lacunes, Brèches, Instabilité, Crétacé inférieur, Crétacé supérieur, Paléocène-Éocène, Kruja, Albanie.

The Late Jurassic Brae oilfields in the South Viking Graben of the northern North Sea contain naturally high concentrations of carbon dioxide (up to 35 mol %). Fields immediately adjacent to the graben bounding fault display the highest concentrations, with CO2 content decreasing eastward into the basin. It is thought the CO2 was introduced into the region via this fault. This thesis examines the possible source of the high CO2 present in the region, focusing on the graben margin fault as a potential conduit for CO2 flux from depth Investigation of cored sections penetrating the graben bounding fault revealed numerous carbonate cemented fracture arrays. The morphology of the fractures and cements is attributed to hydraulic fracturing induced by episodic release of overpressured fluids up the margin fault from depth. Periods of rapid subsidence omnipresent throughout the tectonic history of the graben are conducive to the generation of overpressure; a feature commonly reported in the region. Samples from the carbonate fracture cements were analysed using a host of techniques, including SEM, EMPA, fluid inclusion, and stable δ13C ‐ δ18O analyses. Using SEM analysis, at least five generations of dolomite cement with concomitant iron sulphide were observed. Cement chemistry and textures indicate precipitation from concentrated CO2–rich fluids. A reported high salinity basinal influx from depth concomitant with proposed CO2 charge into the region ~70 Ma is a probable source for the dissolved solids subsequently precipitated as carbonate in the fracture networks. Fluid inclusion analysis provided sufficient evidence to suggest the influx of hot fluids into the region, presumably sourced from deep in the margin fill. Two distinct δ13C vs. δ18O trends are observed in the isotope data from four wells studied. The trends are interpreted as differential mixing between ascending basinal fluids rich in dissolved inorganic carbon and in situ formation waters dominated by organically derived carbon following the onset of thermal decarboxylation in the Kimmeridge Clay Formation. Dissolution of Zechstein carbonates underlying the region is a credible source for the isotopically heavy CO2 found adjacent to the graben margin (δ13CCO2 = ‐2 to ‐5 ‰) and incorporated into the carbonate cements. Inferred variations in fluid mixing from well to well have implications on the variability of fluid flow along the graben margin with respect to contrasting fault morphologies. A Rayleigh fractionation model accommodating CO2 degassing from a hot ascending isotopically heavy fluid can be invoked to explain the observed carbon‐oxygen isotopic covariations in the fracture cements. Geochemical modelling simulating the ascent of CO2‐rich waters suggests degassing has limited impact on precipitation volumes, with fluid‐rock reactions the most likely driver for extensive carbonate mineralisation observed.

Depuis toujours, l'homme a cherché à dater les grands événements de l'histoire de la Terre. Les premières estimations de l'âge de la planète et de la date de l'apparition de l'homme sont données dans des livres sacrés, dont certains datent de plusieurs millénaires. Cependant, les valeurs données dans ces ouvrages minimisent généralement la durée des temps géologiques ; ainsi, la chronologie établie au milieu du XVIIème siècle par l'évêque Ussher à partir de la Bible situe la création de la Terre 4 004 ans avant la naissance du Christ. Cette datation, que l'on sait être aujourd'hui très en dessous de la réalité, a prévalu en Europe jusqu'au XVIIIème siècle environ et des scientifiques tels que Cuvier s'y tenaient. Par la suite, avec les premiers travaux de stratigraphie et de géologie historique, commencèrent à apparaître les rudiments d'une échelle chronostratigraphique globale, basée en grande partie sur l'étude des assemblages de fossiles marins. A la fin du XIXème siècle, après la découverte des premiers restes d'hominidés fossiles, quatre grandes ères géologiques furent distinguées. Parmi celles-ci, l'ère Quaternaire était caractérisée par une faune identique à la faune actuelle et par la présence de l'homme. L'élaboration d'une échelle chronostratigraphique de l'ère Quaternaire a posé et pose un certain nombre de problèmes. En raison de sa courte durée, il est en effet difficile de baser la stratigraphie sur l'évolution des faunes marines, comme c'est le cas pour les autres périodes géologiques, et les chercheurs ont donc tenté successivement pour contourner ce problème d'employer les assemblages paléontologiques continentaux, l'évolution de l'industrie lithique ou des événements géologiques ou climatiques, comme par exemple les témoignages des glaciations. Ce n'est qu'après la seconde guerre mondiale que les progrès de la physique et de la chimie ont fourni les moyens de poser les bases d'une échelle chronologique "absolue" du Quaternaire, avec en particulier le développement des études paléomagnétiques et l'utilisation des techniques de datation basées sur la radioactivité naturelle. Aujourd'hui, le préhistorien, le géographe et le géologue du Quaternaire dispose ainsi d'un certain nombre de méthodes radiométriques ou chimiques, qui sont chacune caractérisées par un domaine d'utilisation précis et qui ne sont applicables qu'à un certain nombre de supports spécifiques.

The pollution of South Africa’s water resources puts a strain on an already stressed natural resource. One of the main pollution sources is industrial effluents such as acid mine drainage (AMD) and other mining effluents. These effluents usually contain high levels of acidity, heavy metals and sulphate. A popular method to treat these effluents before they are released into the environment is lime neutralisation. Although this method is very effective to raise the pH of the effluent as well as to precipitate the heavy metals, it can only partially remove the sulphate. Further treatment is required to reduce the sulphate level further to render the water suitable for discharge into the environment. A number of sulphate removal methods are available and used in industry. These methods can be divided into physical (membrane filtration, adsorption/ion exchange), chemical (chemical precipitation) and biological sulphate reduction processes. A literature study was conducted in order to compare these different methods. The ABC (Alkali – Barium – Calcium) Desalination process uses barium carbonate to lower the final sulphate concentration to an acceptable level. Not only can the sulphate removal be controlled due to the low solubility of barium sulphate, but it can also produce potable water and allows valuable by–products such as sulphur to be recovered from the sludge. The toxic barium is recycled within the process and should therefore not cause additional problems. In this study the sulphate removal process, using barium carbonate as reactant, was investigated. Several parameters have been investigated and studied by other authors. These parameters include different barium salts, different barium carbonate types, reaction kinetics, co–precipitation of calcium carbonate, barium–to–sulphate molar ratios, the effect of temperature and pH. The sulphate removal process was tested and verified on three different industrial effluents. The results and conclusions from these publications were used to guide the experimental work. A number of parameters were examined under laboratory conditions in order to find the optimum conditions for the precipitation reaction to take place. This included mixing rotational speed, barium–to–sulphate molar ratio, initial sulphate concentration, the effect of temperature and the influence of different barium carbonate particle structures. It was found that the reaction temperature and the particle structure of barium carbonate influenced the process significantly. The mixing rotational speed, barium–to–sulphate dosing ratios and the initial sulphate concentration influenced the removal process, but not to such a great extent as the two previously mentioned parameters. The results of these experiments were then tested and verified on AMD from a coal mine. The results from the literature analysis were compared to the experiments conducted in the laboratory. It was found that the results reported in the literature and the laboratory results correlated well with each other. Though, in order to optimise this sulphate removal process, one has to understand the sulphate precipitation reaction. Therefore it is recommended that a detailed reaction kinetic study should be conducted to establish the driving force of the kinetics of the precipitation reactions. In order to upgrade this process to pilot–scale and then to a full–scale plant, continuous reactor configurations should also be investigated. The sulphate removal stage in the ABC Desalination Process is the final treatment step. The effluent was measured against the SANS Class II potable water standard and was found that the final water met all the criteria and could be safely discharged into the environment. / Thesis (M.Ing. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2012.

The pollution of South Africa’s water resources puts a strain on an already stressed natural resource. One of the main pollution sources is industrial effluents such as acid mine drainage (AMD) and other mining effluents. These effluents usually contain high levels of acidity, heavy metals and sulphate. A popular method to treat these effluents before they are released into the environment is lime neutralisation. Although this method is very effective to raise the pH of the effluent as well as to precipitate the heavy metals, it can only partially remove the sulphate. Further treatment is required to reduce the sulphate level further to render the water suitable for discharge into the environment. A number of sulphate removal methods are available and used in industry. These methods can be divided into physical (membrane filtration, adsorption/ion exchange), chemical (chemical precipitation) and biological sulphate reduction processes. A literature study was conducted in order to compare these different methods. The ABC (Alkali – Barium – Calcium) Desalination process uses barium carbonate to lower the final sulphate concentration to an acceptable level. Not only can the sulphate removal be controlled due to the low solubility of barium sulphate, but it can also produce potable water and allows valuable by–products such as sulphur to be recovered from the sludge. The toxic barium is recycled within the process and should therefore not cause additional problems. In this study the sulphate removal process, using barium carbonate as reactant, was investigated. Several parameters have been investigated and studied by other authors. These parameters include different barium salts, different barium carbonate types, reaction kinetics, co–precipitation of calcium carbonate, barium–to–sulphate molar ratios, the effect of temperature and pH. The sulphate removal process was tested and verified on three different industrial effluents. The results and conclusions from these publications were used to guide the experimental work. A number of parameters were examined under laboratory conditions in order to find the optimum conditions for the precipitation reaction to take place. This included mixing rotational speed, barium–to–sulphate molar ratio, initial sulphate concentration, the effect of temperature and the influence of different barium carbonate particle structures. It was found that the reaction temperature and the particle structure of barium carbonate influenced the process significantly. The mixing rotational speed, barium–to–sulphate dosing ratios and the initial sulphate concentration influenced the removal process, but not to such a great extent as the two previously mentioned parameters. The results of these experiments were then tested and verified on AMD from a coal mine. The results from the literature analysis were compared to the experiments conducted in the laboratory. It was found that the results reported in the literature and the laboratory results correlated well with each other. Though, in order to optimise this sulphate removal process, one has to understand the sulphate precipitation reaction. Therefore it is recommended that a detailed reaction kinetic study should be conducted to establish the driving force of the kinetics of the precipitation reactions. In order to upgrade this process to pilot–scale and then to a full–scale plant, continuous reactor configurations should also be investigated. The sulphate removal stage in the ABC Desalination Process is the final treatment step. The effluent was measured against the SANS Class II potable water standard and was found that the final water met all the criteria and could be safely discharged into the environment. / Thesis (M.Ing. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2012.

Started as an EOR technique to produce oil, injection of carbon dioxide which is essentially a greenhouse gas is becoming more and more important. Although there are a number of mathematical modeling studies, experimental studies are limited and most studies focus on injection into sandstone reservoirs as opposed to carbonate ones. This study presents the results of computerized tomography (CT) monitored laboratory experiments to characterize relevant chemical reactions associated with injection and storage of CO2 in carbonate formations. Porosity changes along the core plugs and the corresponding permeability changes are reported for varying CO2 injection rates, temperature and salt concentrations. CT monitored experiments are designed to model fast near well bore flow and slow reservoir flows. It was observed that either a permeability improvement or a permeability reduction can be obtained. The trend of change in rock properties is very case dependent because it is related to distribution of pores, brine composition and as well the thermodynamic conditions. As the salt concentration decreased the porosity and thus the permeability decrease was less pronounced. Calcite scaling is mainly influenced by orientation and horizontal flow resulted in larger calcite deposition compared to vertical flow. The duration of CO2 &ndash / rock contact and the amount of area contacted by CO2 seems to have a more pronounced effect compared to rate effect. The experiments were modeled using a multi-phase, non-isothermal commercial simulator where solution and deposition of calcite were considered by the means of chemical reactions. The calibrated model was then used to analyze field scale injections and to model the potential CO2 sequestration capacity of a hypothetical carbonate aquifer formation. It was observed that solubility and hydrodynamic storage of CO2 is larger compared to mineral trapping.

Little Cedar Creek field is a mature oil field located in southeastern Conecuh County, Alabama, in the northeastern Gulf of Mexico. As of May 2012, 12.5 MMBLS of oil and 14.8 MMCF of natural gas have been produced from the field area. The main reservoirs are microbial carbonate facies and associated nearshore high energy shoal facies of the Upper Jurassic Smackover Formation that overlie conglomerate and sandstone facies of the Norphlet Formation and underlie the argillaceous, anhydritic-carbonaceous facies of the Haynesville Formation. These carbonate reservoirs are composed of vuggy boundstone and moldic grainstone, and the petroleum trap is stratigraphic being controlled primarily by changes in depositional facies. To maximize recovery and investment in the field, an integrated geoscientific-engineering reservoir-wide development plan is needed, including reservoir characterization, modeling, and simulation. This research presents a workflow for geological characterization, formation evaluation, and 3D geologic modeling for fields producing from microbial carbonates and associated reservoirs. The workflow is used to develop a 3D geologic model for the carbonate reservoirs. Step I involves core description and thin section analysis to divide and characterize the different Smackover facies in the field area into 7 units. The main reservoir facies are the microbial boundstone characterized by vuggy porosity and nearshore/shoal grainstone characterized by moldic porosity. Step II is well log correlation and formation evaluation of 113 wells. We use wireline logs and conventional core data analysis data to calculate average porosity values, permeability and water saturations. Neural networks are utilized at this stage to derive permeability where core measurements are absent or partially present across the reservoirs. Step III is building the 3D structural and stratigraphic framework that is populated with the petrophysical parameters calculated in the previous step. Overall, the integration of reservoir characterization, formation evaluation, and 3D geologic modeling provides a sound framework in the establishment of a field/reservoir-wide development plan for optimal primary and enhanced recovery for these Upper Jurassic microbial carbonate and associated reservoirs. Such a reservoir-wide development plan has broad application to other fields producing from microbial carbonate reservoirs.

Thesis (doctoral)--Chalmers Tekniska högskola, 1972. / "Akademisk avhandling för filosofie doktorsexamen i kemi ... fredagen den 2 juni 1972 ... Chalmers tekniska högskola."