scholarly journals Time-Space Characterization of Wellbore-Cement Alteration by CO2-Rich Brine

Geosciences ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 490
Author(s):  
Maria Garcia-Rios ◽  
Philippe Gouze
Keyword(s):  
Numerical Models ◽  
Reaction Rates ◽  
Diffusion Reaction ◽  
Cement Matrix ◽  
Relative Distribution ◽  
Reaction Fronts ◽  
Time Space ◽  
Mass Transfers ◽  
Dissolution And Precipitation ◽  
Diffusion Properties

The risk of CO2 leakage from damaged wellbore is identified as a critical issue for the feasibility and environmental acceptance of CO2 underground storage. For instance, Portland cement can be altered if flow of CO2-rich water occurs in hydraulic discontinuities such as cement-tubing or cement-caprock interfaces. In this case, the raw cement matrix is altered by diffusion of the solutes. This fact leads to the formation of distinctive alteration fronts indicating the dissolution of portlandite, the formation of a carbonate-rich layer and the decalcification of the calcium silicate hydrate, controlled by the interplay between the reaction kinetics, the diffusion-controlled renewing of the reactants and products, and the changes in the diffusion properties caused by the changes in porosity induced by the dissolution and precipitation mechanisms. In principle, these mass transfers can be easily simulated using diffusion-reaction numerical models. However, the large uncertainties of the parameters characterizing the reaction rates (mainly the kinetic and thermodynamic coefficients and the evolving reactive surface area) and of the porosity-dependent diffusion properties prevent making reliable predictions required for risk assessment. In this paper, we present the results of a set of experiments consisting in the alteration of a holed disk of class-G cement in contact with a CO2-rich brine at reservoir conditions (P = 12 MPa and T = 60 °C) for various durations. This new experimental protocol allows producing time-resolved data for both the spatially distributed mass transfers inside the cement body and the total mass transfers inferred from the boundary conditions mass balance. The experimental results are used to study the effect of the fluid salinity and the pCO2 on the overall reaction efficiency. Experiments at high salinity triggers more portlandite dissolution, thinner carbonate layers, and larger alteration areas than those at low salinity. These features are accompanied with different spatial distribution of the alteration layers resulting from a complex interplay between salinity-controlled dissolution and precipitation mechanisms. Conversely, the effect of the pCO2 is more intuitive: Increasing pCO2 results in increasing the overall alteration rate without modifying the relative distribution of the reaction fronts.

CHEMICAL TESSELLATIONS — RESULTS OF BINARY AND TERTIARY REACTIONS BETWEEN METAL IONS AND FERRICYANIDE OR FERROCYANIDE LOADED GELS

2010 ◽  
Vol 20 (07) ◽  
pp. 2241-2252 ◽  
Author(s):  
B. P. J. DE LACY COSTELLO ◽  
I. JAHAN ◽  
P. HAMBIDGE ◽  
K. LOCKING ◽  
D. PATEL ◽  
...  
Keyword(s):  
Metal Ions ◽  
Voronoi Diagram ◽  
Metal Salt ◽  
Voronoi Diagrams ◽  
Reaction Rates ◽  
Cross Reactivity ◽  
Diffusion Reaction ◽  
Reactive Metal ◽  
Simple Chemical ◽  
Pattern Forming

In our recent letter [de Lacy Costello et al., 2009] we described the formation of spontaneous complex tessellations of the plane constructed in simple chemical reactions between drops of metal salts and ferricyanide or ferrocyanide loaded gels. In this paper, we provide more examples of binary tessellations and extend our analysis to tessellations constructed via tertiary mixtures of reactants. We also provide a classification system which describes the tessellation based on the reactivity of the metal salt with the substrate and also the cross-reactivity of the primary products. This results in balanced tessellations where both reactants have equal reactivity or unbalanced tessellations where one reactant has a lower reactivity with the gel. The products can also be partially or fully cross reactive which gives a highly complex tessellation. The tessellations are made up of colored cells (corresponding to different metal ferricyanides or ferrocyanides) separated by bisectors of low precipitate concentration. The tessellations constructed by these reactions constitute generalized Voronoi diagrams. In the case of certain binary or tertiary combinations of reactants where the diffusion/reaction rates differ, then multiplicatively weighted crystal growth Voronoi diagrams are constructed. Where one reactant has limited or no reactivity with the gel (or the products are cross reactive) then the fronts originating from the reactive metal ions cross the fronts originating from the partially reactive metal ions. The fronts can annihilate in the formation of a second Voronoi diagram relating to the relative positions of the reactive drops. Therefore, two or more generalised or weighted Voronoi diagrams can be calculated in parallel by these simple chemical systems. However when these reactions were used to calculate an additively weighted Voronoi diagram (the reaction was initiated at different time intervals) the diagram constructed did not correspond to the theoretical calculation. We use the failure of these reactions to construct an additively weighted Voronoi diagram to prove a mechanism of substrate competition for bisector formation. These tessellations are an important class of pattern forming reactions and are useful in modeling natural pattern forming phenomena in addition to being a great resource for scientific demonstrations.

scholarly journals Measuring reaction rates at equilibrium with the isotope doping method

2019 ◽  
Vol 98 ◽  
pp. 13003
Author(s):  
Chen Zhu ◽  
Yilun Zhang ◽  
J Donald Rimstidt ◽  
Honglin Yuan
Keyword(s):  
Chemical Engineering ◽  
Experimental Testing ◽  
Detailed Balance ◽  
Reaction Rates ◽  
Irreversible Thermodynamics ◽  
Experimental Conditions ◽  
Special Cases ◽  
Wide Range ◽  
Long Time ◽  
Dissolution And Precipitation

Since the time of J. H. van’t Hoff [1], it has been known that chemical equilibrium is dynamic, meaning that at equilibrium, chemical reactions do not cease, but instead the forward and backward reaction rates are equal. The constant concentrations at equilibrium preclude the use of concentrations to measure reaction rates at equilibrium. Therefore, with the exception of a few special cases, no reaction rates at equilibrium have been published in the literature of chemistry, physics, or chemical engineering. Here we report dissolution and precipitation rates at equilibrium for quartz and barite with the isotope-doping method. Experimental data show that dissolution and precipitation rates are equal at equilibrium, indicating the principle of detailed balance (PDB) appear to be applicable at these experimental conditions. The PDB has been a cornerstone for irreversible thermodynamics and chemical kinetics for a long time, and its wide application in geochemistry has mostly been implicit and without experimental testing of its applicability. Nevertheless, many extrapolations based on PDB without experimental validation have far reaching impacts on society’s mega environmental enterprises. The isotope doping method appears to able to test its applicability for a variety of minerals at a wide range of conditions.

scholarly journals A NEW HYBRID APPROACH IN THE CALIBRATION OF BOUSSINESQ-TYPE WAVE BREAKING MODELS

2018 ◽  
pp. 24
Author(s):  
Joaquín Moris ◽  
Patricio Catalán ◽  
Rodrigo Cienfuegos
Keyword(s):  
Wave Height ◽  
Wave Breaking ◽  
Numerical Models ◽  
Hybrid Approach ◽  
Boussinesq Equations ◽  
Water Levels ◽  
Statistical Parameters ◽  
Time Space ◽  
Forcing Mechanisms ◽  
Set Up

Wave breaking is one of the main forcing mechanisms in coastal hydrodynamics, driving mean water levels and currents. Understanding its behavior is key in the goal of improving our comprehension of coastal morphodynamics variations. One way to improve our understanding is through the use of numerical models, such as phase-resolving numerical models based on the Boussinesq equations (Kirby, 2016), which are modified to include breaking by the inclusion of a breaking criteria and a dissipation mechanism. Since there is not a universal law capable of characterizing the wave breaking, the existing models must be calibrated. Traditionally, this is done by adjusting wave height profiles and other free surface statistical parameters without explicitly considering the time-space location and duration of the breaking process. Consequently, it is possible to calibrate a model that accurately represents wave elevation statistics parameters, such as wave height and wave set-up; however, it might not necessarily represent the breaking location-duration and therefore, the forcing.

THE METHOD OF INTER-PARTICLE DISTRIBUTION FUNCTIONS FOR DIFFUSION-REACTION SYSTEMS IN ONE DIMENSION

1995 ◽  
Vol 09 (15) ◽  
pp. 895-919 ◽  
Author(s):  
DANIEL BEN-AVRAHAM
Keyword(s):  
Contact Process ◽  
Reaction Rates ◽  
Distribution Functions ◽  
Diffusion Reaction ◽  
Nonequilibrium Dynamics ◽  
One Dimension ◽  
Many Body ◽  
Dynamical Phase ◽  
Diffusion Limited ◽  
Diffusion Controlled

Diffusions limited reactions in confined geometries exhibit all aspects of nonequilibrium dynamics, such as anomalous kinetics, self-organization and dynamical phase transitions, and have therefore been the subject of extensive research in recent years. In this paper we review the method of interparticle distribution functions (IPDF) which was originally introduced for deriving the exact kinetics of the diffusion-limited coalescence process, A+A→A, in one dimension. We explain the IPDF method and review variants of the coalescence model which can be solved exactly through this technique. We then consider strategies for approximations based on the IPDF method and review applications to coalescence with finite reaction rates (away from the strictly diffusion-controlled regime), many-body reactions (nA→mA), and the contact process. We conclude with a discussion of open, interesting problems and possible ways to their solution.

scholarly journals Supplemental Material: Sustainable densification of the deep crust

2020 ◽  
Author(s):  
Benjamin Malvoisin
Keyword(s):  
Numerical Models ◽  
Bulk Composition ◽  
Coupling Reaction ◽  
Reaction Model ◽  
Diffusion Reaction ◽  
Sensitivity Analyses ◽  
Plagioclase Composition ◽  
Deep Crust ◽  
Inclusion Mapping ◽  
Reaction Fluid

Materials and methods, Figures S1–S9 (fluid-inclusion mapping and point analyses of garnet and clinopyroxene with FTIR, sensitivity analyses for the two numerical models, results of the diffusion-reaction model in open system conditions, X-ray mapping of amphibole inclusions in clinopyroxene, evolution in space of the plagioclase composition), Tables S1 and S2 (chemical composition of the main minerals, and local bulk composition used for numerical modelling), and Movies S1 and S2 (results in 2-D of the model coupling reaction, fluid flow, and deformation).<br>

scholarly journals Supplemental Material: Sustainable densification of the deep crust

2020 ◽  
Author(s):  
Benjamin Malvoisin
Keyword(s):  
Numerical Models ◽  
Bulk Composition ◽  
Coupling Reaction ◽  
Reaction Model ◽  
Diffusion Reaction ◽  
Sensitivity Analyses ◽  
Plagioclase Composition ◽  
Deep Crust ◽  
Inclusion Mapping ◽  
Reaction Fluid

Materials and methods, Figures S1–S9 (fluid-inclusion mapping and point analyses of garnet and clinopyroxene with FTIR, sensitivity analyses for the two numerical models, results of the diffusion-reaction model in open system conditions, X-ray mapping of amphibole inclusions in clinopyroxene, evolution in space of the plagioclase composition), Tables S1 and S2 (chemical composition of the main minerals, and local bulk composition used for numerical modelling), and Movies S1 and S2 (results in 2-D of the model coupling reaction, fluid flow, and deformation).<br>

Time Not Our Time: Physical Controls on the Preservation and Measurement of Geologic Time

2018 ◽  
Vol 46 (1) ◽  
pp. 409-438 ◽  
Author(s):  
Chris Paola ◽  
Vamsi Ganti ◽  
David Mohrig ◽  
Anthony C. Runkel ◽  
Kyle M. Straub
Keyword(s):  
Sedimentation Rate ◽  
Extreme Events ◽  
Numerical Models ◽  
Short Term ◽  
Short Intervals ◽  
Geologic Time ◽  
Time Space ◽  
Stratigraphic Record ◽  
Space Dynamics ◽  
Lines Of Evidence

Sadler's (1981) analysis of how measured sedimentation rate decreases with timescale of measurement quantified the vanishingly small fractional time preservation—completeness—of the stratigraphic record. Generalized numerical models have shown that the Sadler effect can be recovered, through the action of erosional clipping and time removal (the “stratigraphic filter”), from even fairly simple topographic sequences. However, several lines of evidence suggest that most of the missing time has not been eroded out but rather represents periods of inactivity or stasis. Low temporal completeness could also imply that the stratigraphic record is dominated by rare, extreme events, but paleotransport estimates suggest that this is not generally the case: The stratigraphic record is strangely ordinary. It appears that the organization of the topography into a hierarchy of forms also organizes the deposition into concentrated events that tend to preserve relatively ordinary conditions, albeit for very short intervals. Our understanding of time preservation would benefit from insight about how inactivity is recorded in strata; better ways to constrain localized, short-term rates of deposition; and a new focus on integrated time–space dynamics of deposition and preservation.

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