scholarly journals Quantitative Model of the Formation Mechanism of the Rollfront Uranium Deposits

2018 ◽  
Vol 20 (3) ◽  
pp. 213
Author(s):  
D.Y. Aizhulov ◽  
N.M. Shayakhmetov ◽  
A. Kaltayev
Keyword(s):  
Reactive Transport ◽  
Redox Reactions ◽  
Reaction Rates ◽  
Quantitative Model ◽  
Production Costs ◽  
Reactive Flow ◽  
Uranium Deposits ◽  
Geological Processes ◽  
Exploration And Production ◽  
Favorable Conditions

The rollfront type deposits are crescent shaped accumulation of mineralization including uranium, selenium, molybdenum in reduced permeable sandstones. It generally forms within a geochemical barrier between mostly reduced and predominantly oxidized environments. Redox reactions between oxidant and reductant creates favorable conditions for uranium precipitation, while constant flow of oxidant continuously dissolves uranium minerals thereby creating a reactive transport. Several previous works had either focused on the characteristics of the rollfront type deposits, or on the description of chemical and geological processes involved in their genesis. Based on these previous works, authors aimed to mimic laboratory experiments numerically by reactive flow and numerical simulation. Data from one particular experiment was used to determine reaction rates between reactants to produce a model of reactive transport and chemical processes involved in the formation of rollfront type deposits. The resulting model was used to identify the causes of crescent like formations and to determine main mechanisms influencing rollfront evolution. A better understanding and simulation of the mechanism involved in the formation of rollfront type deposits and their properties would contribute to decreased exploration and production costs of commodities trapped within such accumulations. The results of this work can be used to model other deposits formed through infiltration and subsequent precipitation of various minerals at the redox interface.

scholarly journals Pore-Scale Modeling of Mineral Growth and Nucleation in Reactive Flow

2022 ◽  
Vol 3 ◽  
Author(s):  
Vitalii Starchenko
Keyword(s):  
Reactive Transport ◽  
Surface Reaction ◽  
Nucleation Theory ◽  
Crystal Nucleation ◽  
Classical Nucleation Theory ◽  
Reactive Flow ◽  
Natural Environments ◽  
Pore Scale ◽  
Arbitrary Lagrangian Eulerian ◽  
Mineral Precipitation

A fundamental understanding of mineral precipitation kinetics relies largely on microscopic observations of the dynamics of mineral surfaces exposed to supersaturated solutions. Deconvolution of tightly bound transport, surface reaction, and crystal nucleation phenomena still remains one of the main challenges. Particularly, the influence of these processes on texture and morphology of mineral precipitate remains unclear. This study presents a coupling of pore-scale reactive transport modeling with the Arbitrary Lagrangian-Eulerian approach for tracking evolution of explicit solid interface during mineral precipitation. It incorporates a heterogeneous nucleation mechanism according to Classical Nucleation Theory which can be turned “on” or “off.” This approach allows us to demonstrate the role of nucleation on precipitate texture with a focus at micrometer scale. In this work precipitate formation is modeled on a 10 micrometer radius particle in reactive flow. The evolution of explicit interface accounts for the surface curvature which is crucial at this scale in the regime of emerging instabilities. The results illustrate how the surface reaction and reactive fluid flow affect the shape of precipitate on a solid particle. It is shown that nucleation promotes the formation of irregularly shaped precipitate and diminishes the effect of the flow on the asymmetry of precipitation around the particle. The observed differences in precipitate structure are expected to be an important benchmark for reaction-driven precipitation in natural environments.

scholarly journals Phase Separation Can Increase Enzyme Activity by Concentration and Molecular Organization

2020 ◽  
Author(s):  
William Peeples ◽  
Michael K. Rosen
Keyword(s):  
Phase Separation ◽  
Enzymatic Reaction ◽  
Reaction Rates ◽  
Quantitative Model ◽  
Mass Action ◽  
Molecular Organization ◽  
Scaffolding Proteins ◽  
Enzyme Cascade ◽  
Separation Threshold ◽  
Liquid Liquid Phase Separation

AbstractBiomolecular condensates concentrate macromolecules into discrete cellular foci without an encapsulating membrane. Condensates are often presumed to increase enzymatic reaction rates through increased concentrations of enzymes and substrates (mass action), although this idea has not been widely tested and other mechanisms of modulation are possible. Here we describe a synthetic system where the SUMOylation enzyme cascade is recruited into engineered condensates generated by liquid-liquid phase separation of multidomain scaffolding proteins. SUMOylation rates can be increased up to 36-fold in these droplets compared to the surrounding bulk, depending on substrate KM. This dependency produces substantial specificity among different substrates. Analyses of reactions above and below the phase separation threshold lead to a quantitative model in which reactions in condensates are accelerated by mass action and by changes in substrate KM, likely due to scaffold-induced molecular organization. Thus, condensates can modulate reaction rates both by concentrating molecules and by physically organizing them.

Amoco Corporation

2017 ◽  
pp. 1-28
Author(s):  
Susan Chaplinsky ◽  
Luann J. Lynch ◽  
Paul Doherty
Keyword(s):  
Oil Prices ◽  
Cash Flows ◽  
Production Costs ◽  
British Petroleum ◽  
Uncertain Environment ◽  
Exploration And Production ◽  
Future Cash Flows

This case is one of a pair of cases used in a merger negotiation. It is designed to be used with “British Petroleum, Ltd.” (UVA-F-1263). One-half of the class prepares only the British Petroleum (BP) case, and one-half uses this case. BP and Amoco are considering a merger, and are in the process of negotiating a merger agreement. Macroeconomic assumptions, particularly forecasting future oil prices in an uncertain environment, and assumptions about Amoco's ability to reduce exploration and production costs make Amoco's future cash flows difficult to predict.

Evaluation of upstream petroleum agreements and exploration and production costs

OPEC Review ◽  
2005 ◽  
Vol 29 (4) ◽  
pp. 243-266 ◽  
Author(s):  
Abdulaziz Al-Attar ◽  
Osamah Alomair
Keyword(s):  
Production Costs ◽  
Exploration And Production

Mechanisms of multiphase reactive flow using biogenically calcite-functionalized micromodels

Lab on a Chip ◽  
2018 ◽  
Vol 18 (24) ◽  
pp. 3881-3891 ◽  
Author(s):  
Wen Song ◽  
Folake Ogunbanwo ◽  
Marianne Steinsbø ◽  
Martin A. Fernø ◽  
Anthony R. Kovscek
Keyword(s):  
Reactive Transport ◽  
Reactive Flow ◽  
Reaction Products ◽  
Storage Media ◽  
Protective Reaction

Biogenically calcite-functionalized microfluidics reveals a new grain-engulfment mechanism where protective reaction products alter reactive transport through porous CO2 storage media.

Impact of chaotic mixing on reactive transport: experiment in porous media at high Pe and Da

2021 ◽  
Author(s):  
Hugo Sanquer ◽  
Joris Heyman ◽  
Tanguy Le Borgne ◽  
Khalil Hanna
Keyword(s):  
Porous Media ◽  
Reactive Transport ◽  
3D Imaging ◽  
Fluid Phase ◽  
Reaction Rates ◽  
Transport Processes ◽  
Chaotic Mixing ◽  
Pore Scale ◽  
Chemical Gradients ◽  
The Impact

<p>Solute transport in porous media plays a key role in a range of chemical and biological processes, including contaminant degradation, precipitation, dissolution and microbiological dynamics. Increasing evidences have shown that the conventional complete mixing assumption at the pore scale can lead to a strong overestimation of reaction rates. Recent 3D imaging experiments of mixing in porous media suggest that these pore scale chemical gradients may be sustained by chaotic mixing dynamics. However, the consequences of such chaotic mixing on reactive processes are unknown.</p><p>In this work, we use reactive transport experiments coupled to 3D imaging to investigate the impact of micro-scale chaotic flows on mixing-limited reactions in the fluid phase.  We use optical index matching and laser-induced fluorescence to characterize the pore scale distribution of reactive product concentration for a range of Peclet and Damkhöler numbers. We use these measurements to develop a reactive lamellar theory that quantifies the impact of pore scale chemical gradients induced by chaotic mixing on effective reaction rates. These results provide new perspectives for upscaling reactive transport processes in porous media.</p>

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