Navegando por Assunto "Carbonate"

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Acesso aberto (Open Access)
Flora e fauna do neógeno das áreas de manguezais de lagoas costeiras da plataforma equatorial do Brasil: processo de piritização
(Universidade Federal do Pará, 2021-04-02) MATA, Giovanni Alvaro Teixeira da; AGUILERA SOCORRO, Orangel Antonio; http://lattes.cnpq.br/5854051483674293; https://orcid.org/0000-0003-4418-8351
The carbonate-siliciclastic rocks from the early to middle Miocene Pirabas Formation in the equatorial margin of Brazil show a brackish ecofacies of mangrove and coastal lagoons paleoenvironments under tidal influence. The studied section has dark mudstone at the top, characterized by a microbial methanogenesis zone where pyritized trunks, leaves, micro- and macrofossils, and trace fossils, have been investigated. The petrographic characterization and crystallographic analyses distinguish mostly framboids crystal for trunk fragments to the octahedric and cubic crystals from invertebrate shells. The geochemistry analyzes revealed that Fe and S are concentrated both in the fossiliferous content of invertebrate constituents and in the matrix that hosts the trunk, while the other elements are mainly linked to invertebrates. The preferential distribution of these elements is in accordance with the presence of FeS2 compounds replacing fossils, reflecting the anoxic and reducing conditions of the environment. The pyrite-rich lithostratigraphic section was deposited in a shallow water environment, where pyrite mineralization was developed during the early diagenetic stage under anoxic conditions, plenty of organic matter, warm and mixohaline water. The integration of faciological, stratigraphic and chemical data from the carbonate deposits of the Pirabas Formation, in addition to reconstructing the stratigraphic behavior of these units in the period studied, would also assist in understanding the paleoenvironmental and paleogeographic changes of the Bragantina Platform and its possible relationship with global events.
Acesso aberto (Open Access)
Influência do transporte advectivo no processo de dissolução de rochas carbonáticas em ácido clorídrico.
(Universidade Federal do Pará, 2024-04-30) COSTA, Brenda Matos da; SILVA, Daniel; AUM, Pedro Tupã Pandava; http://lattes.cnpq.br/7515419219571335
Carbonate rock stimulation is a technique used in the petroleum industry to increase the productivity index of wells by increasing the permeability of a region close to the well. In acidification, an acid is injected into the reservoir rock. In carbonate rocks, the acid interacts with the rock to promote dissolution. The acid-rock occurrence is characterized by being essentially heterogeneous due to the different phases of the reactants. The quantification of occurrence taxa in heterogeneous systems is complex, as it involves a combination of several variables that are relevant to the manifestation of transport. The way in which acid interacts with the porous medium can be analyzed using various techniques and equipment that can help with understanding. The most common equipment is the Rotating Disk Apparatus (RDA), which consists of a reactor, which can operate different pressure and temperature ranges and different rotations. However, due to the difficulty of acquiring this type of equipment, several experiments have been reported using alternative methodologies. Thus, this work aims to study how measuring the reaction rate using different methodologies can influence the result. A comparative experimental study was conducted using three different methodologies, namely, static dissolution, dynamic dissolution, and rotating disk, to measure the impact of mineralogy, porosity, rotation speed, and pressure applied to the reaction system. The focus is to evaluate to what extent the results of the static and dynamic dissolution experiments diverge from the experiments conducted with the rotating disk, which is considered the standard for this type of analysis. In general, it was observed that increasing rotation promotes an increase in the reaction rate of 10.36% from static to dynamic at 100 RPM and 63.07% from static to dynamic at 500 RPM for Indiana limestone, a similar behavior was observed for other mineralogies. Additionally, from obtaining the diffusion coefficient in the process of dynamic dissolution and rotating disk of 3.75x10^-5 and 9.13x10^-5, respectively, for coquina samples, it was evidenced that the absence of pressure in the system hinders the mass transfer process due to the presence of CO2 (g), thus underestimating the diffusion in the carbonate – HCl system.