O Campo de Camorim é um dos principais produtores de hidrocarbonetos da Bacia de Sergipe (SE), situada na porção nordeste da margem continental brasileira. Foram estudados quatro poços com testemunhagem no Membro Carmópolis (da Formação Muribeca) que é considerado como o melhor reservatório do Campo. Os poços posicionamse em dois blocos estruturais (aqui denominados de Área Leste e Área Oeste) que apresentam comportamentos distintos em relação à recuperação de hidrocarbonetos. O Membro Carmópolis caracteriza-se pelo predomínio de conglomerados e litoarenitos de granulometria média a grossa (Área Oeste) e também fina a muito fina (Área Leste). Estas rochas se depositaram sob condições climáticas de semi-aridez, na fase transicional de evolução da margem continental brasileira. A cimentação dolomítica teve um importante papel na qualidade destes reservatórios principalmente pela sustentação do arcabouço. Normalmente, a porosidade é reduzida pela compactação e deformação de fragmentos líticos originando uma pseudomatriz. Em função da evolução diagenética observada na área de estudo, foram identificados três tipos de cimento dolomítico. O Tipo I (dolomita romboédrica microcristalina, intergranular, eogenética) apresenta-se livre de ferro. A dolomita Tipo II, com óxido de ferro (“aspecto sujo”), é caracterizada pela forma de mosaicos (anédricos). No estágio mesodiagenético, caracteriza-se o Tipo III identificado pelos romboedros com zoneamento entre dolomita, dolomita ferrosa e anquerita, pois há com maior disponibilidade do íon ferro no ambiente. Em relação aos valores δ18O e δ13C observa-se que para a Área Oeste, considerando-se o predomínio da influência de águas meteóricas, podem ser calculados valores de 54,9oC a 70,0oC para a precipitação da dolomítica (Tipos I e II). Este intervalo de temperatura associa-se aos arenitos cimentados próximo da superfície e de soterramento raso. Para as amostras da Área Leste propõe-se a atuação de fluidos marinhos e, neste caso, o range da temperatura de precipitação variou de 78,8oC a 102,8oC. Este intervalo de temperatura corresponderia os cimentos de precipitação pós-compactacional associados às maiores profundidades. / The Camorim Field is one of the principal producers of hydrocarbon in the Sergipe Basin (SE), situated in the northeastern portion of the eastern Brazilian continental shore. Four well cores were studied in the Carmópolis Member (from the Muribeca Formation), which is considered the best reservoir in the Field. The wells are positioned in two structural blocks (here denominated as East Area and West Area) that present distinct behavior relating to hydrocarbon recuperation. The Carmópolis Member is characterized by a predominance of conglomerates and lithoarenites with medium and thick granulometry (West Area) and also fine and very fine (East Area). These rocks were deposited under semi-arid conditions, in the transitional phase of the Brazilian continental coast evolution. Dolomitic cementation had an important role in the quality of these reservoirs principally due to supporting the framework. Normally, the porosity is reduced by the compacting and deformity of lithic fragments from a pseudomatrix. Due to the diagentic evolution observed in the studied area, three types of dolomotic cement were found. Type I (microcrystalline romboedric dolomite, intergranular, eogenetic) is free of iron. The Type II dolomite, with iron oxide (“dirty look”), is characterized by it mosaic form (anedric). In the mesodiagenetic phase, Type III is characterized, identified by romboedros with zoning between dolomite, iron dolomite, and anquerite, since there are more iron ions in the environment. In relation to the values δ18O e δ13C, it was observed that for the West Area, considering the predominance of meteoric water influence, the values 54.9oC to 70.0oC can be calculated for dolomite precipitation (Types I and II). This temperature interval is associated to the cemented arenites close to the surface. For the samples from the East Area, marine fluid action is proposed, and in this case, the precipitation temperature range varied from 78.8oC to 102.8oC. This temperature interval would correspond to the post-compact precipitation cements associated to greater depths.

O Campo de Camorim é um dos principais produtores de hidrocarbonetos da Bacia de Sergipe (SE), situada na porção nordeste da margem continental brasileira. Foram estudados quatro poços com testemunhagem no Membro Carmópolis (da Formação Muribeca) que é considerado como o melhor reservatório do Campo. Os poços posicionamse em dois blocos estruturais (aqui denominados de Área Leste e Área Oeste) que apresentam comportamentos distintos em relação à recuperação de hidrocarbonetos. O Membro Carmópolis caracteriza-se pelo predomínio de conglomerados e litoarenitos de granulometria média a grossa (Área Oeste) e também fina a muito fina (Área Leste). Estas rochas se depositaram sob condições climáticas de semi-aridez, na fase transicional de evolução da margem continental brasileira. A cimentação dolomítica teve um importante papel na qualidade destes reservatórios principalmente pela sustentação do arcabouço. Normalmente, a porosidade é reduzida pela compactação e deformação de fragmentos líticos originando uma pseudomatriz. Em função da evolução diagenética observada na área de estudo, foram identificados três tipos de cimento dolomítico. O Tipo I (dolomita romboédrica microcristalina, intergranular, eogenética) apresenta-se livre de ferro. A dolomita Tipo II, com óxido de ferro (“aspecto sujo”), é caracterizada pela forma de mosaicos (anédricos). No estágio mesodiagenético, caracteriza-se o Tipo III identificado pelos romboedros com zoneamento entre dolomita, dolomita ferrosa e anquerita, pois há com maior disponibilidade do íon ferro no ambiente. Em relação aos valores δ18O e δ13C observa-se que para a Área Oeste, considerando-se o predomínio da influência de águas meteóricas, podem ser calculados valores de 54,9oC a 70,0oC para a precipitação da dolomítica (Tipos I e II). Este intervalo de temperatura associa-se aos arenitos cimentados próximo da superfície e de soterramento raso. Para as amostras da Área Leste propõe-se a atuação de fluidos marinhos e, neste caso, o range da temperatura de precipitação variou de 78,8oC a 102,8oC. Este intervalo de temperatura corresponderia os cimentos de precipitação pós-compactacional associados às maiores profundidades. / The Camorim Field is one of the principal producers of hydrocarbon in the Sergipe Basin (SE), situated in the northeastern portion of the eastern Brazilian continental shore. Four well cores were studied in the Carmópolis Member (from the Muribeca Formation), which is considered the best reservoir in the Field. The wells are positioned in two structural blocks (here denominated as East Area and West Area) that present distinct behavior relating to hydrocarbon recuperation. The Carmópolis Member is characterized by a predominance of conglomerates and lithoarenites with medium and thick granulometry (West Area) and also fine and very fine (East Area). These rocks were deposited under semi-arid conditions, in the transitional phase of the Brazilian continental coast evolution. Dolomitic cementation had an important role in the quality of these reservoirs principally due to supporting the framework. Normally, the porosity is reduced by the compacting and deformity of lithic fragments from a pseudomatrix. Due to the diagentic evolution observed in the studied area, three types of dolomotic cement were found. Type I (microcrystalline romboedric dolomite, intergranular, eogenetic) is free of iron. The Type II dolomite, with iron oxide (“dirty look”), is characterized by it mosaic form (anedric). In the mesodiagenetic phase, Type III is characterized, identified by romboedros with zoning between dolomite, iron dolomite, and anquerite, since there are more iron ions in the environment. In relation to the values δ18O e δ13C, it was observed that for the West Area, considering the predominance of meteoric water influence, the values 54.9oC to 70.0oC can be calculated for dolomite precipitation (Types I and II). This temperature interval is associated to the cemented arenites close to the surface. For the samples from the East Area, marine fluid action is proposed, and in this case, the precipitation temperature range varied from 78.8oC to 102.8oC. This temperature interval would correspond to the post-compact precipitation cements associated to greater depths.

O refratário dolomítico é amplamente utilizado como revestimento de trabalho para panelas no processo de Aciaria, por sua excelente refratariedade em condições de serviço, principalmente em usinas que produzem aços acalmados ao silício. O emprego deste refratário é em virtude de uma formação natural de uma capa protetora, a qual potencializa a vida do refratário, acarretando em um aumento da vida útil do equipamento. O trabalho baseia-se em um estudo comparativo entre dois tijolos dolomíticos nomeados aqui como tijolos A e B. Os testes em escala industrial foram dados pela montagem de seis revestimentos, de cada tijolo, colocados sob as mesmas condições, monitorando-se a temperatura e o grau de oxidação do banho metálico. Ao final da campanha da panela se realizou alguns testes POST MORTEM, onde se destaca as medidas dos residuais. Além disso, para completar este estudo comparativo, separaram-se tijolos novos de cada marca, os quais foram submetidos às análises microestruturais via MEV, análises termogravimétricas, análises químicas por EDS e DRX, entre outros ensaios. Os resultados mostraram que o tijolo A teve um desempenho 20% superior ao tijolo B. O tijolo A tem maior pureza, microestrutura com agregados arredondados, com maior homogeneidade, uma ótima distribuição entre partículas finas e médias, favorecendo o empacotamento o que justifica sua maior tenacidade à fratura e resistência à corrosão. Também foi evidenciada de forma clara a presença de carbono grafite no tijolo A, conferindo-lhe uma maior resistência ao choque térmico e à corrosão. / The refractory dolomite is widely used as coating for ladles work in steelmaking process for its excellent refractoriness in terms of service. The use of this refractory is due to a natural formation of a protective layer, which enhances the life of the refractory, resulting in increased equipment life. This work is based on a comparative study between two bricks dolomite named here as A and B. Tests were given on an industrial scale by assembling six coatings of each brick placed in the same conditions by monitoring the temperature and the degree of oxidation of the metal bath. At the end of the campaign applied some tests POST MORTEM, how measurements of residual stresses. Moreover, to complete this comparative study, separated from each brand new bricks, which were subjected to microstructural analyzes via MEV, thermogravimetric analysis, chemical analysis by EDS and XRD, among other tests. The results showed that the performance of brick A was 20% higher than brick B. The Brick A has a higher purity, microstructure with rounded aggregates with greater homogeneity, optimal distribution between fine and medium particles, favoring the packaging which justifies a higher fracture toughness and corrosion resistance. It was also clearly evidenced the presence of graphitic carbon in the brick A, giving it a higher resistance to thermal shock and corrosion.

The North Wales Platform, UK, represents a lower Carboniferous carbonate platform that developed during back-arc extension on the northern margin of the Wales-Brabant Massif. This succession was faulted and folded during the Late Carboniferous Variscan Orogeny and again during the Late Jurassic extension-Tertiary Alpine Orogeny, resulting in multiple reactivations of Caledonian structural trends (N-S, NE-SW and NW-SE) and basin inversion. The platform underwent deformation, several episodes of fluid-flow, and multiple phases of diagenetic overprinting. The products of fluid circulation in this area consist of the Mississippi Valley-type (MVT) mineralisation and dolomitisation, mostly affecting the carbonates of the lower Carboniferous (Dinantian) succession. This study presents a combined regional sedimentological, diagenetic and structural framework through multiscale, interdisciplinary techniques. Techniques include field observation, transmitted light and cathodoluminescence analysis, in-situ and bulk major and trace element analysis including rare earth elements, stable isotope (oxygen/carbon), and strontium isotope analysis. The North Wales Dinantian (Asbian-Brigantian) succession developed from a ramp to rimmed platform geometry and records a range of depositional and non depositional environments including platform margin, subtidal, peritidal and emergent. Early diagenesis comprises a series of marine and meteoric calcite cements. These are volumetrically the most important cements and occlude nearly all primary interparticle porosity on the North Wales Platform. Consequently, burial calcite cements and MVT mineralisation was precipitated within fractures and dissolution-enhanced secondary porosity. Dolomitisation on the North Wales Platform occur as pods along the current day coastline/palaeo platform margin and eight dolomite phases have been identified. These are present as matrix replacive and cement phases that are spatially and temporally related to deep seated structural lineaments. It is proposed that early diagenesis resulted from the establishment of meteoric aquifers, influenced by tectono-eustatic fluctuations. Subsequently, small volumes of fluid were released following compaction and during the waning stages of lower Carboniferous extension. The onset of the Variscan compression during the mid – Late Carboniferous led to the main stage of basin de-watering on to the platform via faults/fracture systems and the development of pockets of overpressuring. Circulating marine pore-waters provided the necessary magnesium required for dolomitisation within select fault/fracture systems. A second phase of tectonic deformation with associated copper mineralisation occurred during the Triassic-Jurassic extension and Alpine uplift. Fluids and metals for the copper mineralisation were derived from the adjacent siliciclastic Permo-Triassic and Jurassic East Irish Sea Basin succession. Compared to the adjacent and time equivalent Derbyshire and Askrigg Platforms, the North Wales Platform displays a more complex paragenesis as a result of differing burial histories and fluid sources. This study highlights the importance of understanding palaeo-fluid flow and diagenesis in platform carbonates and is directly relevant to hydrocarbon production, mining and resource containment in reservoirs.

An estimated 2.5 million people live on dolomite and in excess of 1.2 billion Rands of property damage has been observed to date and in excess of 800 sinkholes have occurred in the Southern Tshwane area alone. Research on dolomitic terrain is hence crucial in the quest for releasing land for development that is deemed safe from a dolomite risk perspective. This thesis attempts to present a better understanding of the geology and stability of a carefully selected type area east of Irene town in Pretoria, Gauteng, South Africa, and to interrogate the current method of dolomite stability analysis. The study area is located partly on the Lyttelton and Eccles Formations, Malmani Subgroup, Chuniespoort Group, of the Transvaal Supergroup. The Transvaal Supergroup rocks were subjected to complex faulting and folding along the northeastern rim of the Johannesburg Dome. Displacement and duplication of the Transvaal rocks by faulting is common to the east and south east of Pretoria with the karst topography being well developed along these water exploited structural features. The karst development, in particular on the Eccles Formation, has lead to a highly variable dolomite and chert bedrock topography. Cavernous conditions can be expected both within the bedrock and the overburden. A summary is given of how instability occurs. Given sufficient time and the correct triggering mechanisms, instability may occur naturally but is expedited, by many orders of magnitude, by man’s activities. Various authors have over the years attempted to classify dolomitic land. The “method of scenario supposition for stability evaluation of sites on dolomitic land in South Africa”, which has been applied widely by the industry, certainly since 1995, was applied to the study area in 1996/7. The method was successful in focussing the attention of investigators of dolomitic land on the various factors that contribute to instability. However, with time it became evident that modification and further clarification of various concepts was necessary. The modified method was named “method for dolomite land hazard and risk assessment in South Africa”. This method was applied and comparison drawn between the two assessments. The latest investigative and evaluative methodology is explained. The gravity method as applied to dolomite studies is explained and its results interrogated. Shallow dolomite and its associated risks are analyzed. The karst types identified by Waltham and Fookes is considered and compared to the karst identified in the study area and in so doing placed in a South African context. The results of the new assessment are placed in context with current development type and density recommendations. The functions and requirements of the National Home Builders Registration Council are explained. It is concluded that the study area can be divided into 3 broad risk zones. Zone A represents the shallow dolomite areas and largely reflects a high risk of small to medium-size sinkholes and dolines with localized sub-areas reflecting a high risk of large sinkholes (i.e. inherent risk classes 5,3, 6 (7)). Zone B represents areas potentially reflecting a low to medium risk of up to large sinkholes and dolines (i.e. inherent risk classes 1 and 4). Here bedrock is relatively deep (40 m) and mantled by relatively thick stable material. Zone C represents transitional areas between shallow and deep bedrock where bedrock topography is often highly undulating and thick sequences of low density insoluble weathering product and cavernous conditions occur. Here the risk of all size sinkholes and dolines is high (inherent risk classes 5, 6, 7 and 8). The function of water precautionary measures and founding solutions is discussed. It is pointed out that these measures and solutions cannot change the inherent risk classification but rather change the development risk. Under certain circumstances an acceptable development risk may be established, however a stumbling block remains quality of workmanship, practicality of implementation and costs, the latter referring to the costs of some founding solutions, which render many developments unfeasible. Significant financial losses due to dolomite stability are recorded annually. The development present in this study area is 9 years old and already severe damage to structures have been observed. Despite the mounting costs associated with dolomite instability, local authorities and developers continue to develop dolomitic land. Sites such us these will continue to be targeted for development and investigators are under increasing pressure to come up with engineering solutions to the problem. It is essential to continue to better understand the sites earmarked for development from a geological perspective, so as not to leave future generations with large tracts of sterilized land and a community having to deal with injury to life and limb and fearful of dolomite. Many a geologist may continue to discover various generations of weathering products in this study area in the future and continue to grapple with the links between dolomite stability or rather lack thereof, the geotechnical properties of the various weathering products and the effects of geological structures. Copyright / Dissertation (MSc (Engineering and Environmental Geology))--University of Pretoria, 2007. / Geology / unrestricted

No description available.

From the analysis of fossils, using the cathodoluminescence technique, it is seen that there is a pattern to the luminescence colours exhibited by dolomite, calcite and quartz, depending on the amount of the trace element Mn2+ present in the structure of the minerals. In the experiment dolomite luminesces turquoise blue, calcite luminesces pale pink & bright red, & quartz luminesces sea blue. The calcite and quartz colours agree well with the observation of both Agrell et al. (1965) and Sippel et al. (1965). However, the dolomite luminescence colour definitely agrees better with the colour described by Agrell et al. than with that observed by Sippel et al. Selective replacement of material occurs in Rugosa corals of the Devonian Onondaga formation of Southern Ontario. Quartz replacing material in the cavities of fossils is common, with the fringe wall of the fossil being of calcite as was previously observed by Middleton (1958). The matrix around the fossils consists mainly of quartz and calcite with minor dolomite. A systematic difference in style of replacement (with respect to the various heights from which the fossils came in the section) occurred when considering replacement of the fossils by quartz. Replacement of calcite by quartz followed by slight dolomitization of the matrix in the Onondaga is suggested by luminescence observation. Also suggested by luminescence observations is: 1) Dolomitization by a downward influx of Mg2+ ions, and 2) Homogenous and heterogenous micritic mud fillings in Rugosa corals' cavities. / Thesis / Bachelor of Science (BSc)

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