Effects of end-member sediments on CO2 hydrate formation: Implications for geological carbon storage

Fines migration and clogging in porous media have significant implications for engineering applications. For example, during the extraction of marine gas hydrates, fines migration can lead to pore clogging and reduced permeability. This study combines micromodel experiments with DEM-CFD simulations to investigate the effects of fine type (latex/mica), fine shape (spherical/flake), pore size (50 to 700 μm), and pore fluid composition (DW/brine) on fines migration, fine clogging behavior, and the evolution of host sediment porosity. Experiments demonstrate that clogging is geometrically influenced by the relationship between pore size and fines dimensions. Even when the size of fines (mica) is smaller than the pore throat size, their aggregates can still lead to clogging at very low concentrations (0.1–0.2%). The aggregate size of irregular mica is affected by changes in pore fluid properties, which may occur due to the freshening of pore water during hydrate dissociation. Furthermore, a moving gas/liquid interface concentrates fines, thereby increasing the risk of pore clogging. Simulations further reveal that fines migration causes dynamic changes in porosity, which requires a comprehensive consideration of the coupled effects of fine type, fluid velocity, pore size, and fluid chemistry. This study elucidates the microscopic mechanisms and quantifies the macroscopic effects of fines migration behavior in porous media, providing a theoretical foundation for further research.

The Bay of Campeche is located in a region of moderate to high seismic activity related to the active triple junction between the North American, Caribbean, and Cocos plate boundaries. Therefore, the fixed offshore platforms and subsea structures in the Bay of Campeche must be designed against earthquake loading. A database was developed of classification and index properties tests, in situ measurements of shear wave velocity (Vs) using downhole P-S suspension seismic velocity logging, in situ piezocone penetration tests, resonant column tests to characterize the shear modulus and material damping ratio at small shear strains (10−5 % to about 0.1 %), and strain-controlled cyclic direct simple shear tests to evaluate the decrease of shear modulus and the increase of material damping ratio at large shear strains (0.1 % to about 10 %) performed on sand from the Bay of Campeche, including sands with no carbonate content to 100 % carbonate content, retrieved from the seafloor to a penetration depth of 120 m below seafloor. The database was tailored specifically to develop empirical correlations for the Bay of Campeche sand to determine Vs when in situ measurements of Vs are not available and to develop numerical modeling to predict the variation of the normalized shear modulus (G/Gmax) and material damping ratio (D) as a function of shear strains (g) when dynamic test results are unavailable for all the sand layers. The equations developed to calculate Vs and the curves of G/Gmax-g and D-g of Bay of Campeche sands are recommended for preliminary or perhaps even final seismic site response evaluations.

Particle migration is a pore-scale process that fundamentally controls pore-structure evolution and seepage behavior in granular porous media. This study investigates fine particles migration in coarse-grained sediments and its effects on pore structure and permeability by combining low-field nuclear magnetic resonance (LF-NMR) experiments with coupled CFD–DEM simulations. The evolution of fine particles migration rate, porosity variation, and permeability was analyzed under different fluid injection velocities and fines concentrations. Higher injection velocities accelerate fines initiation and early-stage migration by increasing hydrodynamic drag forces, whereas their influence diminishes at later stages due to pore-structure confinement and localized particle retention. At a constant injection velocity, increasing fines concentration suppresses early fines mobilization owing to enhanced interparticle interactions and pore throat blockage. As seepage continues, progressive fines release and export enlarge pore space and enhance permeability. Spatial analyses reveal that fines migration is governed by localized retention and rearrangement within pore throats. Within the investigated parameter ranges and timescales, system evolution is dominated by internal erosion and pore unclogging rather than sustained macroscopic clogging. These results provide mechanistic experimental–numerical insight into fines migration and seepage stability in granular porous media, with direct relevance to hydrate-bearing sediments and other fine-sensitive geological systems.

Rock fatigue damage and instability during failure processes involve continuous initiation, propagation, and coalescence of internal cracks accompanied by energy exchange with surroundings. Energy-based analysis provides fundamental insights into damage accumulation and transformation mechanisms. This paper systematically review the research progress on energy evolution patterns under various influencing factors, microstructural transformation mechanisms during damage development, and associated macroscopic mechanical behaviors. It synthesizes achievements in energy-based strength criteria, fatigue damage evolution models, constitutive relationships, and engineering stability assessments. Current limitations are identified, and future directions are proposed: 1) Investigating energy evolution mechanisms under multi-field coupling conditions; 2) Developing comprehensive energy-driven damage evolution laws and constitutive models; 3) Establishing energy-based fatigue life prediction frameworks for rock engineering applications. These advancements aim to enhance theoretical understanding and practical reliability in rock mechanics analysis.

The Bay of Campeche is located in a region of moderate to high seismic activity related to the active triple junction between the North American, Caribbean, and Cocos plate boundaries. Therefore, the fixed offshore platforms and subsea structures in the Bay of Campeche must be designed against earthquake loading. A database was developed of classification and index properties tests, in situ measurements of shear wave velocity using downhole P-S suspension seismic velocity logging, in situ piezocone penetration tests, resonant column tests to characterize the shear modulus and material damping ratio at small shear strains (10−5 % to about 0.1 %), and strain-controlled cyclic direct simple shear tests to evaluate the decrease of shear modulus and the increase of material damping ratio at large shear strains (0.1 % to about 10 %) performed on clays from the Bay of Campeche, including clays with no carbonate content to 100 % carbonate content, retrieved from the seafloor to a penetration depth of 120 m below seafloor. The database was tailored specifically to develop empirical correlations for the Bay of Campeche clay to determine Vs when in situ measurements of Vs are not available and to develop numerical modeling to predict the variation of the normalized shear modulus (G/Gmax) and material damping ratio as a function of shear strains (g) when dynamic test results are unavailable for all the clay layers. The equations developed to calculate Vs and the curves of G/Gmax-g and D-g of Bay of Campeche clays are recommended for preliminary or perhaps even final seismic site response evaluations. La Bahía de Campeche se encuentra en una región de moderada a alta actividad sísmica relacionada con la triple unión activa entre los límites de las placas de América del Norte, el Caribe y la de Cocos. Por lo tanto, las plataformas fijas en alta mar y las estructuras submarinas en la Bahía de Campeche deben diseñarse contra la carga sísmica. Una base de datos de pruebas de clasificación y propiedades índice, mediciones in situ de la velocidad de la onda de corte Vs utilizando la sonda suspendida, pruebas in situ de piezocono penetrómetro (PCPT), pruebas de columna resonante para caracterizar el módulo de rigidez y la relación de amortiguación del material a bajas deformaciones angulares(10-5 % a aproximadamente 0.1 %) y pruebas cíclicas de corte simple directo (DSS) con deformación controlada para evaluar la disminución del módulo de rigidez y el aumento de la relación de amortiguación del material a deformaciones angulares altas (0.1 % a aproximadamente 10 %) realizados en arcillas de la Bahía de Campeche incluyendo arcillas sin contenido de carbonato hasta el 100% del contenido de carbonato recuperados desde el fondo marino y hasta a una profundidad de 120 m por debajo del fondo marino. La base de datos fue diseñada específicamente para desarrollar para las arcillas de la Bahía de Campeche correlaciones empíricas para determinar Vs, cuando no se dispone de mediciones in situ de Vs, y modelos numéricos para predecir la variación del módulo de rigidez normalizado (G/Gmax) y la relación de amortiguamiento de materiales en función de la deformación angular (g) cuando no hay resultados de pruebas dinámicas disponibles para todas las capas de arcilla. Las ecuaciones desarrolladas para calcular Vs, y las curvas de G/Gmax-g y D-g de las arcillas de la Bahía de Campeche se recomiendan para evaluaciones preliminares o tal vez incluso finales de respuesta sísmica del sitio.