Search

Hydration and dehydration reactions play pivotal roles in plate tectonics and the deep water cycle, yet many facets of (de)hydration reactions remain unclear. Here, we study (de)hydration reactions where associated solid density changes are predominantly balanced by porosity changes, with solid rock deformation playing a minor role. We propose a hypothesis for three scenarios of (de)hydration front propagation and test it using one‐dimensional hydro‐mechanical‐chemical models. Our models couple porous fluid flow, solid rock volumetric deformation, and (de)hydration reactions described by equilibrium thermodynamics. We couple our transport model with reactions through fluid pressure: the fluid pressure gradient governs porous flow and the fluid pressure magnitude controls the reaction boundary. Our model validates the hypothesized scenarios and shows that the change in solid density across the reaction boundary, from lower to higher pressure, dictates whether hydration or dehydration fronts propagate: decreasing solid density causes dehydration front propagation in the direction opposite to fluid flow while increasing solid density enables both hydration and dehydration front propagation in the same direction as fluid flow. Our models demonstrate that reactions can drive the propagation of (de)hydration fronts, characterized by sharp porosity fronts, into a viscous medium with zero porosity and permeability; such propagation is impossible without reactions, as porosity fronts become trapped. We apply our model to serpentinite dehydration reactions with positive and negative Clapeyron slopes and granulite hydration (eclogitization). We use the results of systematic numerical simulations to derive a new equation that allows estimating the transient, reaction‐induced permeability of natural (de)hydration zones. Plain Language Summary: We investigate reactions of hydration, which is the incorporation of water into a rock, and dehydration, which is the liberation of water from a rock, with simple mathematical models. These reactions are critical in understanding processes like plate tectonics, but many aspects of how hydration or dehydration fronts move through a rock are unclear. Our research focuses on reactions where changes in density are mostly balanced by changes in pore space, termed porosity, rather than the deformation of the solid rock. We developed mathematical models that combine fluid flow, rock deformation, and hydration/dehydration reactions. We derived simple equations that predict changes in porosity during hydration and dehydration, even when the solid rock deforms simultaneously. We found that whether a rock hydrates or dehydrates depends on how its solid density changes with increasing pressure during the reaction. By systematically studying our model, we discovered that the speed of hydration and dehydration is not influenced by the interval of fluid pressure over which the reaction occurs or the relationship between porosity and permeability. We present an equation that can be used to estimate permeability from natural (de)hydration zones. Key Points: (De)hydration fronts propagate into zero‐permeability rock if the solid density of the reactant is smaller than the one of the productExternal fluid flux compensates the imbalance between fluid generated/consumed by reaction and fluid needed to fill generated porosityResults of systematic numerical simulations allow estimating the transient, reaction‐induced permeability of natural (de)hydration zones [ABSTRACT FROM AUTHOR]

The interplay between compaction‐driven fluid flow and plastic yielding within porous media is investigated through numerical modeling. We establish a framework for understanding the dynamics of fluid flow in deforming porous materials that corresponds to the equations describing solitary porosity wave propagation. A concise derivation of the coupled fluid flow and poro‐viscoelastoplastic matrix behavior is presented, revealing a connection to Biot's equations of poroelasticity and Gassmann's theory in the elastic limit. Our findings demonstrate that fluid overpressure resulting from channelized fluid flow initiates the formation of new shear zones. Through three‐dimensional simulations, we observe that the newly formed shear zones exhibit a parabolic shape. Furthermore, plasticity exerts a significant influence on both the velocity of fluid flow and the shape of fluid channels. Importantly, our study highlights the potential of spontaneous channeling of porous fluids to trigger seismic events by activating both new and pre‐existing faults. Plain Language Summary: In this study, we looked at how fluids move through porous rocks and how they interact with the solid frame of the rocks. The physics was explored in two‐ and three‐dimensions by leveraging the power of high‐performance computing (HPC) based on graphical processing units (GPU). We found that two key processes occur at the same time: fluid flow gets concentrated into channels due to the changing pressure and interaction with the solid material, and it also forms dike‐like structures as it pushes into newly formed shear zones. Importantly, our study highlights the potential of spontaneous channeling of porous fluids to trigger seismic events by activating both new and pre‐existing faults. This research underscores the complex relationship between fluid flow dynamics and geomechanical processes, offering insights into the mechanisms underlying earthquake initiation. Key Points: We present the numerical modeling of fully coupled fluid flow and poro‐viscoelastoplastic matrix flow with decompaction weakeningWe show that fluid overpressure at the tip of the fluid flow channel triggers the development of non‐symmetric shear bandsWe discover that plastic yielding accelerates the fluid flow and modifies the fluid flow pattern [ABSTRACT FROM AUTHOR]

Shear strain localization refers to the phenomenon of accumulation of material deformation in narrow slip zones. Many materials exhibit strain localization under different spatial and temporal scales, particularly rocks, metals, soils, and concrete. In the Earth's crust, irreversible deformation can occur in brittle as well as in ductile regimes. Modeling of shear zones is essential in the geodynamic framework. Numerical modeling of strain localization remains challenging due to the non‐linearity and multi‐scale nature of the problem. We develop a numerical approach based on graphical processing units (GPU) to resolve the strain localization in two and three dimensions of a (visco)‐hypoelastic‐perfectly plastic medium. Our approach allows modeling both the compressible and incompressible visco‐elasto‐plastic flows. In contrast to symmetric shear bands frequently observed in the literature, we demonstrate that using sufficiently small strain or strain rate increments, a non‐symmetric strain localization pattern is resolved in two‐ and three‐dimensions, highlighting the importance of high spatial and temporal resolution. We show that elasto‐plastic and visco‐plastic models yield similar strain localization patterns for material properties relevant to applications in geodynamics. We achieve fast computations using three‐dimensional high‐resolution models involving more than 1.3 billion degrees of freedom. We propose a new physics‐based approach explaining spontaneous stress drops in a deforming medium. Plain Language Summary: Strain localization is the accumulation of strain in narrow regions of rocks and other materials like metals, soils, and concrete, occurring at different scales. The strength of most geomaterials, particularly rocks, is strongly pressure‐dependent, with strength increasing with increasing pressure. We developed efficient numerical algorithms using High‐Performance Computing (HPC) and graphical processing units (GPUs) to model strain localization in 2D and 3D for applications in geodynamics and earthquake physics. Unlike previous models, our method reveals non‐symmetrical patterns by using very small strain increments, highlighting the need for high‐detail modeling. We found that elasto‐plastic and visco‐plastic models show similar strain patterns for relevant materials. Our method also achieves fast, detailed computations with over 1.3 billion variables and offers a new explanation for sudden stress drops in deforming materials. Key Points: We resolve material instability during deformation resulting in a non‐symmetric pattern of strain localizationWe demonstrate the similarity in patterns of strain localization between frictional and time‐dependent plasticity modelsWe achieve fast numerical simulations in high‐resolution model setups in three dimensions involving more than 500 million degrees of freedom [ABSTRACT FROM AUTHOR]

The ramped temperature oxidation (RTO) test is a screening method used to assess the stability of a reservoir for air-injection Enhanced Oil Recovery (EOR) and to evaluate the oxidation behavior of oil samples. It provides valuable kinetic data for specific cases. The RTO test allows for the analysis of various characteristics, such as temperature evolution, peak temperatures, oxygen uptake, carbon dioxide generation, oxidation and combustion front velocity, recovered and burned hydrocarbons, and residual coke. The adaptation of RTO experiments to in situ combustion (ISC) modeling involves validation and history matching based on numerical simulation of RTO tests, using 3D digital models of experimental setup. The objective is to estimate the kinetic parameters for a customized reaction model that accurately represents ISC. Within this research, the RTO test was provided for bitumen samples related to the Samara oil region. A 3D digital model of the RTO test is constructed using CMG STARS, a thermal hydrodynamic simulator. The model is designed with multiple layers and appropriate heating regimes to account for uncertainties in the experimental setup and to validate the numerical model. The insulation of the setup affects radial heat transfers and helps to control the observed temperature levels. The modified traditional reaction model incorporates thermal cracking of Asphaltenes, low-temperature oxidation (LTO) of Asphaltenes and Maltenes, and high-temperature combustion of coke. Additionally, the model incorporates high-temperature combustion of light oil in the vapor phase, which is generated through Asphaltenes cracking and LTO reactions. [ABSTRACT FROM AUTHOR]

A lot of processes in rock mechanics are far from being understood today despite all the advancements in the current modelling technologies. Even more, as far as we know, the progress in some geomechanical disciplines became much slower than 20 or even 10 years ago. That paradox is because of the fact that in last decades researches and engineers were often happy enough with mutually unrelated approaches: geochemistry, geomechanics and reservoir hydrodynamics were not considered as three components of one compound. Now people understood that it should do this but they can not, simply because each of the processes become complicated too much and there is no theory, or, at least an approach, which would simplify them consistently. In what follows we propose such an approach. To be more specific, we present the next step in our modeling which is based on a unified approach for reactive-thermal-fluid transport in deforming porous media. The way we treat the thermal coupled fluid flow, rock nonlinear deformation and chemical reactions are suitable for prediction of geological and petroleum processes at different scales, such as oil and gas migration, CO2 capture and storage, physical, chemical, and thermal EOR optimization. The model takes into account multi-phase fluid flow, all main nonlinear processes in a visco-elastic-plastic porous matrix, and treats porosity and permeability evolution. However, the main emphasis in the present study is put on reactions, which may be either homogeneous or heterogeneous.Reactions are calculated based on Gibbs minimization technique allowing for any possible reaction for considered chemical species at local equilibrium. Partitioning between components in fluid and solid phases are also caused by the diffusion of chemical species and phase flow leading to changes in composition, thereby self-consistently accounting for local effective composition which is then used in the calculation of thermodynamic equilibrium. The proposed method was verified against the standard flash procedure in the case when Gibbs potential is derived from an equation of state; the set of classical examples from reacting gas dynamics; and classical solutions for a shock-induced detonation process and slow combustion. After that, the technique was validated against experiments in the combustion tube and applied to fundamental and industrial problems. The brightest examples of the studies are in-situ combustion during an unconventional oil field development and laboratory investigation of oil oxidation processes and combustion front propagation during the experiments in combustion tube. We will show also how do some of them work. [ABSTRACT FROM AUTHOR]