Geomechanical stability of the caprock during CO2 sequestration in deep saline aquifers

8 páginas, 5 figuras.Sequestration of carbon dioxide (CO2) in deep saline aquifers has emerged as a mitigation strategy for reducing greenhouse gas emissions to the atmosphere. The large amounts of supercritical CO2 that need to be injected into deep saline aquifers may cause large fluid pressure buildup. The resulting overpressure will produce changes in the effective stress field. This will deform the rock and may promote reactivation of sealed fractures or the creation of new ones in the caprock seal, which could lead to escape paths for CO2. To understand these coupled hydromechanical phenomena, we model an axisymmetric horizontal aquifer-caprock system. We study plastic strain propagation patterns using a viscoplastic approach. Simulations illustrate that plastic strain may propagate through the whole thickness of the caprock if horizontal stress is lower than vertical stress. In contrast, plastic strain concentrates in the contact between the aquifer and the caprock if horizontal stress is larger than vertical stress. Aquifers that present a low-permeability boundary experience an additional fluid pressure increase once the pressure buildup cone reaches the outer boundary. However, fluid pressure does not evolve uniformly in the aquifer. While it increases in the low-permeability boundary, it drops in the vicinity of the injection well because of the lower viscosity of CO2. Thus, caprock stability does not get worse in semi-closed aquifers compared to open aquifers. Overall, the caprock acts as a plate that bends because of pressure buildup, producing a horizontal extension of the upper part of the caprock. This implies a vertical compression of this zone, which may produce settlements instead of uplift in low-permeability (k≤10-18 m2) caprocks at early times of injection.V.V. would like to acknowledge the Spanish Ministry of Science and Innovation (MIC) for financial support through the “Formación de Profesorado Universitario” program. V.V. also wishes to acknowledge the “Colegio de Ingenieros de Caminos, Canales y Puertos – Catalunya” for their financial support. This project has been funded by the Spanish Ministry of Science and Innovation through the project CIUDEN (Ref.: 030102080014), and through the MUSTANG project, from the European Community’s Seventh Framework Programme FP7/2007-2013 under grant agreement nº 227286.Peer reviewe

Технічний проект будинкового газопостачання житлового району м. Харків з удосконаленням конструкції регулятора тиску газу

Практичні результати: – виконано аналіз об’єкту газифікації; – розроблено проект газопостачання району населеного пункту; – удосконалено конструкцію регулятора тиску газу; – проведено аналіз з охорони праці та навколишнього середовища.Мета роботи – розробка проекту газопостачання району населеного пункту м. Харків з удосконаленням конструкції регулятора тиску газу

pH-Controlled Exponential and Linear Growing Modes of Layer-by-Layer Assemblies of Star Polyelectrolytes

A novel solventless sample preparation, stir-bar sorptive extraction (SBSE), for extraction, and sample enrichment of organic compounds from biological fluids, is described in this manuscript from principle to applications. The SBSE is based on sorptive extraction, whereby the compounds are extracted into a polymer coating, polydimethylsiloxane (PDMS), on a magnetic stirring rod. The extraction is controlled by the partitioning coefficient of drugs between the PDMS and sample matrix, and upon the sample-extraction medium phase ratio. The SBSE technique has been applied successfully, with high sensitivities, to biomedical analysis of volatiles and for semi-volatiles drugs from biological sample, including urine, plasma, and saliva. SBSE combined with in situ derivatization, drugs quite more polar (e.g. metabolites) also can be analyzed

Influence of Polyplex Formation on the Performance of Star-Shaped Polycationic Transfection Agents for Mammalian Cells

Genetic modification (“transfection”) of mammalian cells using non-viral, synthetic agents such as polycations, is still a challenge. Polyplex formation between the DNA and the polycation is a decisive step in such experiments. Star-shaped polycations have been proposed as superior transfection agents, yet have never before been compared side-by-side, e.g., in view of structural effects. Herein four star-shaped polycationic structures, all based on (2-dimethylamino) ethyl methacrylate (DMAEMA) building blocks, were investigated for their potential to deliver DNA to adherent (CHO, L929, HEK-293) and non-adherent (Jurkat, primary human T lymphocytes) mammalian cells. The investigated vectors included three structures where the PDMAEMA arms (different arm length and grafting densities) had been grown from a center silsesquioxane or silica-coated γ-Fe2O3-core and one micellar structure self-assembled from poly(1,2-butadiene)-block PDMAEMA polymers. All nano-stars combined high transfection potential with excellent biocompatibility. The micelles slightly outperformed the covalently linked agents. For method development and optimization, the absolute amount of polycation added to the cells was more important than the N/P-ratio (ratio between polycation nitrogen and DNA phosphate), provided a lower limit was passed and enough polycation was present to overcompensate the negative charge of the plasmid DNA. Finally, the matrix (NaCl vs. HEPES-buffered glucose solution), but also the concentrations adjusted during polyplex formation, affected the results