The Impact of Wettability on Dynamic Fluid Connectivity and Flow Transport Kinetics in Porous Media

Petrophysical Evaluation of a Shaly Sandstone Reservoir and the Effect of Clay Minerals on Reservoir Quality: A Case Study from the Barremian Mengo Sandstone, Kouilou Basin, Republic of Congo

The growing global demand for energy is driving specialists to reevaluate and exploit fossil fuel deposits previously considered economically unviable. This study addresses the challenge of evaluating the Mengo shaly sandstone reservoir, a fan sandstone that is affected by diagenesis and that has heterogeneous porosity and low permeability and was abandoned due to its poor petrophysical properties, in the Kouilou Basin, Republic of Congo, particularly the impact of clay minerals on reservoir quality. The significance of this study lies in addressing the complex challenges associated with evaluating and exploiting shaly sandstone reservoirs, which are increasingly important for meeting global energy demands. The study involved integrating well logs, core data, and well testing data from 14 wells, with a focus on seven, using techniques such as the Schlumberger Techlog software; gamma ray, density, neutron, sonic, and resistivity logs; core analysis to measure porosity, permeability, and lithology; Xray diffraction; and scanning electron microscopy for mineral identification. The results indicated a reservoir composition of poorly sorted coarse and fine-grained lithologies with a significant clay content. Chlorite was identified as the primary clay mineral affecting porosity and permeability, with porosity values ranging from 8 to 15% and permeability values averaging from 0.16 to 1.68 mD. The study identifies diagenetic processes, such as the presence of clay minerals, as the primary cause of the contrast between porosity and permeability by reducing reservoir quality. Despite the challenges posed by the high clay content and radioactivity, integrating log and core data into a conceptual geological model is crucial for accurate reservoir characterization. The Midfan area around the MEN-105 well is pinpointed as the most favorable zone for future drilling.

Advancements in Glass Fiber Separator Technology for Lithium-Sulfur Batteries: The Role of Transport, Material Properties, and Modifications

Lithium-sulfur batteries (LSBs) are widely regarded as a promising next-generation energy storage technology due to their exceptional theoretical capacity and energy density. However, their commercialization has been hindered by challenges such as the polysulfide shuttle effect and poor reaction kinetics, which limit efficiency and cycle life. This review delves into the critical aspects of LSB technology, beginning with an overview of the fundamental mechanisms and challenges. The role of transport in porous media is analyzed, particularly in relation to its impact on ion mobility, sulfur utilization, and overall battery performance. Key criteria for separator design are then explored, emphasizing the importance of multifunctional separators in mitigating polysulfide diffusion, enhancing electrochemical stability, and prolonging cycle life. Glass fiber (GF) separators are highlighted for their intrinsic properties, including thermal stability and electrolyte wettability, which make them ideal candidates for modification. Various modification techniques are reviewed, demonstrating how functional coatings and advanced materials can transform GF separators into highly efficient components of Li-S batteries. By integrating novel approaches to separator modification, significant improvements in performance and cycling stability are achieved. The outlook and future directions in this research field are also given.

Pore-Scale Study of Fluid Displacement in Parallel-Layered Porous Media and Implications of Associated Distinct Flow Dynamics

Fluid displacement within layered porous media is more complex than in nonlayered ones. Most of the previous studies placed a focus on the porous media with layerings perpendicular to the flow direction, and the effects of pore topology were often ignored. Therefore, this study aims to reveal the flow physics in porous media with layering parallel to the flow direction by accounting for the specific pore topology. Based on the phase-field method, a series of pore-scale numerical simulations were performed to investigate the dynamic displacement processes within layered porous media under various capillary numbers and wettability. The results showed that oil recovery was strongly affected by the heterogeneity of porous media in the capillary fingering regime compared to the viscous one. Besides, the alternative advancing phenomenon of the water fingers was suppressed in layered porous media. Compared with water wetting conditions, the viscous fingering regime of the invading water is more pronounced under oil wetting conditions. Last but not least, the center of mass of water flow paths can be used for fingering regime identification. These findings contribute to our better understanding of the flow dynamics of fluid displacement within layered porous media, which are of great significance to the industry related to oil recovery, underground storage of carbon dioxide and hydrogen gas, etc.

Factors influencing residual air saturation during consecutive imbibition processes in an air-water two-phase fine sandy medium - A laboratory-scale experimental study

The residual air saturation plays a crucial role in modeling hydrological processes of groundwater and the migration and distribution of contaminants in subsurface environments. However, the influence of factors such as media properties, displacement history, and hydrodynamic conditions on the residual air saturation is not consistent across different displacement scenarios. We conducted consecutive drainage-imbibition cycles in sand-packed columns under hydraulic conditions resembling natural subsurface environments, to investigate the impact of wetting flow rate, initial fluid state, and number of imbibition rounds (NIR) on residual air saturation. The results indicate that residual air saturation changes throughout the imbibition process, with variations separated into three distinct stages, namely, unstable residual air saturation (Sgr-u), momentary residual air saturation (Sgr-m), and stable residual air saturation (Sgr). The results also suggest that the transition from Sgr-u to Sgr is driven by changes in hydraulic pressure and gradient; the calculated values followed the following trend: Sgr > Sgr-u > Sgr-m. An increase in capillary number, which ranged from 1.46 × 10-7 to 3.07 × 10-6, increased Sgr-u and Sgr-m in some columns. The increase in Sgr ranged from 0.034 to 0.117 across all the experimental columns; this consistent increase can be explained by water film expansion at the primary wetting front along with a strengthening of the hydraulic gradient during water injection. Both the pre-covered water film on the sand grain surface and a pore-to-throat aspect ratio of up to 4.42 were identified as important factors for the increased residual air saturation observed during the imbibition process. Initial air saturation (Sai) positively influenced all three types of residual air saturation, while initial capillary pressure (Pci) exhibited a more pronounced inhibitory effect on residual air saturation, as it can partly characterized the initial connectivity of the air phase generated under different drying flow rates. Under identical wetting flow rate conditions, Sgr was higher during the second imbibition than during the first imbibition due to variations in initial fluid state, involving both fluid distribution and the concentration of dissolved air in the pore water. In contrast, NIR did not have an obvious effect on the three types of residual air saturation. This work aims to provide empirical evidences and offer further insights into the capture of non-wetting phases in groundwater environments, as well as to put forward some potential suggestion for future investigations on the retention and migration of contaminants that involves multiphase interface interactions in subsurface environments.

Wettability of Graffiti Coatings by Green Nanostructured Fluids

Green nanostructured fluids (GNFs), specifically water-in-oil nanoemulsions (w/o NEs), were investigated as professional "brush on, wipe off" nanodetergents for the effective removal of various challenging graffiti coatings. The efficacy of the advanced nanodetergents in eradicating resilient graffiti coatings was evaluated using various methods to assess the surface properties of forming graffiti coatings. The surface properties of these coatings were examined by assessing their wettability by water, surface free energy, and topography to obtain information on the intermolecular interactions with the nanodetergent during the wetting and graffiti removal process. Our findings revealed significant variations in the coating removal rate and efficacy of green nanostructured fluids, which are stabilized using surfactants derived from saccharides or amino acids. A water-in-oil nanoemulsion, stabilized by caprylyl/capryl glucoside, demonstrated exceptional efficiency at cleaning graffiti paints based on alkyd resin and containing various additives such as nitrocellulose or bitumen, from any hard surface within a short time period. However, a w/o NE, stabilized by sodium cocoyl glycinate, also showed effective removal of graffiti paints containing durable bitumen, albeit at a slower rate on. These green nanostructured fluids can be used as specific nanodetergents for the comprehensive removal of various graffiti coatings, but require a specified action time to prevent damage to the original substrate beneath the paint coating.