By combining the micellar templating in nanometer-scale with the polymerization-induced phase separation in micrometer-scale, we can synthesize monolithic silica or silsesquioxane gel materials with hierarchical well-defined macropores and shape-controlled mesopores. Depending on the mechanism of enhancing micellar-templating of siloxane oligomers, macroframeworks containing long-range-ordered cylindrical mesopores with different degrees of order have been produced. Alkylene-bridged silicon alkoxides can also be prepared into similarly hierarchical porous structures with broadened variations in framework morphology. These examples demonstrate the versatility of using phase-separation in micellartemplated gelling systems to obtain well-defined macroporous structures.

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Hydraulic fracturing is an important technique in the development of enhanced geothermal systems and unconventional resources. Although the fracture modes induced by hydraulic fracturing influence the recovery efficiency of the resources, the current understanding of this relationship is insufficient. In this study, we considered the acoustic emissions (AEs) induced during hydraulic fracturing under uniaxial loading conditions in the laboratory, and applied a moment tensor analysis by carefully correcting the coupling condition and directivity of AE transducers. Experiments were conducted for two types of Kurokami-jima granite samples: those with a rift plane perpendicular (Type H) or parallel (Type V) to the expected direction of fracture propagation (i.e. along the loading axis). In the experiments, both sample types experienced a significant number of shear, tensile and compressive events. The dominant fracture mode for Type H samples is found to be tensile events in which the fracture plane is parallel to the loading axis, whereas for Type V samples, shear events are dominant. This difference suggests that the dominant fracture modes induced by hydraulic fracturing are highly dependent on the relationship between the direction of fracture propagation and orientation of pre-existing weak planes.

In development of unconventional reservoirs such as tight and shale oil/gas reservoirs, hydraulic fracturing has been applied to enhance reservoir productivity. In spite of active applications of hydraulic fracturing, a shape of induced fractures is not fully understood. This paper presents the result of laboratory visualization experiment of hydraulic fracturing, which was conducted to visualize the shape of induced factures with cylindrical shale sample through the fluorescent method. An acrylic resin mixed with a fluorescent agent was used as a fracturing fluid. The resin is solidified and fixed within the samples by heat. The shape of the induced facture reveals based on different brightness under ultraviolet light irradiation. Many associated microfractures were observed around the main fractures. The fracturing fluid can be trapped in these types of microfractures by capillary force and these fractures cause lower recovery of fracturing fluid in the actual field operations. Acoustic emission (AE) was also monitored by the 16 sensors mounted the rock samples. Result from the path of main fractures identified by the resin mixed with a fluorescent substance and distribution of AE indicates good agreement between two. This helps us to examine which particular failure generates microseismicity. Although the scale difference between laboratory experiments and field operations needs to be taken into account, the shape of induced fractures is successfully characterized. We interpret the fluid leak off zone, main fracture, and branch fractures can be a source of the AE while no AE is observed at the area of the fracture with large aperature based on overlaying AE hypocenters with visualized induced fracture. This work helps engineers to make a proper model of hydraulic fractures for the estimation of well productivity.