Borehole cement sheath integrity - numerical simulation under reservoir conditions

The most important function of the cement sheath is to provide zonal isolation in a production well. To achieve this objective, a hydraulic seal must be obtained between the casing and the cement, and between the cement and the formation. Throughout the life of a production well the cement sheath is subject to different reservoir conditions. Drilling, changes in pressure and temperature due to production, stimulation, and natural tectonic activity can lead to cement damage. Smaller chronic leakages due to defective well tubulars or damaged cement sheaths in the well cause a loss in the sustained casing pressure (SCP). Ensuring well integrity means to protect the environment against leakage along the well and to guarantee its producing potential. The tool presented in the current paper allows the cement engineer to simulate underground well conditions. After simulating the chosen scenario, various outputs can be combined in the overall analysis, including compression, traction, thermo-elasticity, and microannulus to help the cement engineer to analyze and design the proper cement to be used during the completion process.Publicado en: Mecánica Computacional vol. XXXV, no. 5Facultad de Ingenierí

Borehole cement sheath integrity - numerical simulation under reservoir conditions

The most important function of the cement sheath is to provide zonal isolation in a production well. To achieve this objective, a hydraulic seal must be obtained between the casing and the cement, and between the cement and the formation. Throughout the life of a production well the cement sheath is subject to different reservoir conditions. Drilling, changes in pressure and temperature due to production, stimulation, and natural tectonic activity can lead to cement damage. Smaller chronic leakages due to defective well tubulars or damaged cement sheaths in the well cause a loss in the sustained casing pressure (SCP). Ensuring well integrity means to protect the environment against leakage along the well and to guarantee its producing potential. The tool presented in the current paper allows the cement engineer to simulate underground well conditions. After simulating the chosen scenario, various outputs can be combined in the overall analysis, including compression, traction, thermo-elasticity, and microannulus to help the cement engineer to analyze and design the proper cement to be used during the completion process.Publicado en: Mecánica Computacional vol. XXXV, no. 5Facultad de Ingenierí

Borehole cement sheath integrity - numerical simulation under reservoir conditions

The most important function of the cement sheath is to provide zonal isolation in a production well. To achieve this objective, a hydraulic seal must be obtained between the casing and the cement, and between the cement and the formation. Throughout the life of a production well the cement sheath is subject to different reservoir conditions. Drilling, changes in pressure and temperature due to production, stimulation, and natural tectonic activity can lead to cement damage. Smaller chronic leakages due to defective well tubulars or damaged cement sheaths in the well cause a loss in the sustained casing pressure (SCP). Ensuring well integrity means to protect the environment against leakage along the well and to guarantee its producing potential. The tool presented in the current paper allows the cement engineer to simulate underground well conditions. After simulating the chosen scenario, various outputs can be combined in the overall analysis, including compression, traction, thermo-elasticity, and microannulus to help the cement engineer to analyze and design the proper cement to be used during the completion process.Publicado en: Mecánica Computacional vol. XXXV, no. 5Facultad de Ingenierí

Crisis económica y reorganización del espacio industrial.

Sin resume

Application of an unsteady flamelet model in a RANS framework for spray A simulation

[EN] In the present investigation the Spray A reference configuration defined in the framework of the Engine Combustion Network (ECN) has been modeled by means of an Unsteady Flamelet Model (USFM) including detailed parametric studies to evaluate the impact of ambient temperature, oxygen concentration and density. The study focuses on the analysis of the spray ignition delay, the flame lift-off length and the internal structure of the spray and flame according to the experimental information nowadays available for validating the results provided by the model. Promising results are obtained for the nominal case and also for the parametric variations (temperature, oxygen...) in terms of liquid and vapor penetration, ignition delay (ID) and lift-off length (LOL). The model permits to predict the ID and the LOL which constitute two parameters of key importance for describing the characteristics of transient reacting sprays. Valuable insight on the details of the combustion process is obtained from the analysis of formaldehyde (CH2O), acetylene (C2H2) and hydroxide (OH) species in spatial coordinates and also in the so-called phi-T maps. Important differences arise in the inner structure of the flame in the quasi-steady regime, which is closely linked to soot formation, when varying the ambient boundary conditions. Additionally, the auto-ignition process is investigated in order to describe in detail the spatial onset and propagation of combustion. Results confirm the impact of the ambient conditions on the regions of the spray where start of combustion takes place, so the relation between the local scalar dissipation rate and mixture fraction variance is also discussed. This investigation provides an insight of the potential of the USFM combustion model to describe the physical and chemical processes involved in transient spray combustion.Authors acknowledge that this work was possible thanks to the Ayuda para la Formacion de Profesorado Universitario (FPU 14/03278) belonging to the Subprogramas de Formacion y de Movilidad del Ministerio de Educacion, Cultura y Deporte from Spain. Also this study was partially funded by the Ministerio de Economia y Competitividad from Spain in the frame of the COMEFF (TRA2014-59483-R) national project.Desantes, J.; García-Oliver, JM.; Novella Rosa, R.; Pérez-Sánchez, EJ. (2017). Application of an unsteady flamelet model in a RANS framework for spray A simulation. Applied Thermal Engineering. 117:50-64. https://doi.org/10.1016/j.applthermaleng.2017.01.101S506411

Influence of the n-dodecane chemical mechanism on the CFD modelling of the diesel-like ECN Spray A flame structure at different ambient conditions

[EN] Encouraged by the diversity of n-dodecane chemical mechanisms currently available, this investigation focuses on analysing the impact of using different fuel oxidation schemes on the diesel-like Engine Combustion Network (ECN) Spray A flame structure, simulated by means of an Unsteady Flamelet Progress Variable (UFPV) combustion model. The present research discusses systematically the characteristics of four n-dodecane chemical mechanisms in perfectly stirred reactors and counterflow laminar diffusion flames (flamelets) before the final evaluation in turbulent reacting sprays in order to describe the effects of adding different physical levels of complexity to the ignition of the mixtures. In addition, this analysis is complemented with the description of the effect of the boundary conditions on the flame structure. Results evidence the extreme importance of the low temperature chemistry including the period for which the cool flame extends. The different prediction of this stage between mechanisms leads to noticeable different laminar flame structures which in turn produce substantially distinct turbulent flames, especially in the vicinity of the lift-off length (LOL) in terms of reactivity and positioning in the Z-T map. Finally, simulations confirm the strong effect of the boundary conditions, especially for the ambient temperature, on the ignitable mixtures which directly impacts on the soot precursors formation. (C) 2019 The Combustion Institute. Published by Elsevier Inc. All rights reserved.Authors acknowledge that this work was possible thanks to the Ayuda para la Formacion de Profesorado Universitario (FPU 14/03278) belonging to the Subprogramas de Formacion y de Movilidad from the Ministerio de Educacion, Cultura y Deporte from Spain. This work was partially funded by the Government of Spain through CHEST Project (TRA2017-89139-C2-1-R).Payri, F.; García-Oliver, JM.; Novella Rosa, R.; Pérez-Sánchez, EJ. (2019). Influence of the n-dodecane chemical mechanism on the CFD modelling of the diesel-like ECN Spray A flame structure at different ambient conditions. Combustion and Flame. 208:198-218. https://doi.org/10.1016/j.combustflame.2019.06.032S19821820

Electrochemical behaviour of copper in aqueous moderate alkaline media, containing sodium carbonate and bicarbonate, and sodium perchlorate

The voltammetric polarization of Cu specimens in Na2CO3, NaHCO3 and NaClO4 solutions (8-12pH range) has been investigated. Voltammetry data were complemented with SEM and electron microprobe analysis. Results are found to be in agreement with the passivation model developed for Cu in plain NaOH solutions. For the latter the process can be described in terms of two steps, namely, at low potentials the initial formation of a Cu2O thin layer followed by the growth of a massive Cu2O layer, and at higher potentials the appearance of a CuO-Cu(OH)2 layer. These processes are accompanied by the formation of soluble Cu species. Beyond a certain potential which increases with the solution pH, copper pitting takes place. This model can be extended to Cu in carbonate/bicarbonate containing solutions by considering that Cu carbonates precipitate as long as soluble ionic Cu species are produced, without interfering appreciably with the formation of Cu oxides. The appearance of copper carbonate species is enhanced when pitting corrosion sets in. The precipitation of Cu carbonates occurs principally around pits. Cu pitting, although it is observed for all solutions, becomes more noticeable at the lowest pH values. At a constant pH, the density of pits increases in the order NaClO4 > NaHCO3 > Na2CO3. The influence of the electrolyte composition on Cu pitting is closely related to the blockage capability for pit nucleation and growth of the corresponding copper salts. Passivation in the Cu2O-Cu(OH)2 region hinders pitting corrosion.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA)Facultad de Ciencias Exacta

Electrochemical behaviour of copper in aqueous moderate alkaline media, containing sodium carbonate and bicarbonate, and sodium perchlorate

The voltammetric polarization of Cu specimens in Na2CO3, NaHCO3 and NaClO4 solutions (8-12pH range) has been investigated. Voltammetry data were complemented with SEM and electron microprobe analysis. Results are found to be in agreement with the passivation model developed for Cu in plain NaOH solutions. For the latter the process can be described in terms of two steps, namely, at low potentials the initial formation of a Cu2O thin layer followed by the growth of a massive Cu2O layer, and at higher potentials the appearance of a CuO-Cu(OH)2 layer. These processes are accompanied by the formation of soluble Cu species. Beyond a certain potential which increases with the solution pH, copper pitting takes place. This model can be extended to Cu in carbonate/bicarbonate containing solutions by considering that Cu carbonates precipitate as long as soluble ionic Cu species are produced, without interfering appreciably with the formation of Cu oxides. The appearance of copper carbonate species is enhanced when pitting corrosion sets in. The precipitation of Cu carbonates occurs principally around pits. Cu pitting, although it is observed for all solutions, becomes more noticeable at the lowest pH values. At a constant pH, the density of pits increases in the order NaClO4 > NaHCO3 > Na2CO3. The influence of the electrolyte composition on Cu pitting is closely related to the blockage capability for pit nucleation and growth of the corresponding copper salts. Passivation in the Cu2O-Cu(OH)2 region hinders pitting corrosion.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA)Facultad de Ciencias Exacta