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©2016. American Geophysical Union. All Rights Reserved. We conducted hydraulic fracturing (HF) experiments on 170 mm cubic granite specimens with a 20 mm diameter central hole to investigate how fluid viscosity affects HF process and crack properties. In experiments using supercritical carbon dioxide (SC-CO2), liquid carbon dioxide (L-CO2), water, and viscous oil with viscosity of 0.051–336.6 mPa · s, we compared the results for breakdown pressure, the distribution and fracturing mechanism of acoustic emission, and the microstructure of induced cracks revealed by using an acrylic resin containing a fluorescent compound. Fracturing with low-viscosity fluid induced three-dimensionally sinuous cracks with many secondary branches, which seem to be desirable pathways for enhanced geothermal system, shale gas recovery, and other processes.

© 2015, Springer-Verlag Wien. We performed hydraulic fracturing experiments on cylindrical cores of anisotropic shale obtained by drilling normal to the sedimentary plane. Experiments were conducted under ambient condition and uniaxial stresses, using three types of fracturing fluid: viscous oil, water, and liquid carbon dioxide (L-CO2). In the experiments using water and oil, cracks extended along the loading direction normal to the sedimentary plane under the uniaxial loading and extended along the sedimentary plane without loading. These results suggest that the direction of crack extension is strongly affected by in situ stress conditions. Fluorescent microscopy revealed that hydraulic fracturing with viscous oil produced linear cracks with few branches, whereas that with water produced cracks with many branches inclining from the loading axis. Statistical analysis of P wave polarity of acoustic emission waveforms showed that viscous oil tended to induce Mode I fracture, whereas both water and L-CO2 tended to induce Mode II fracture. Crack extension upon injection of L-CO2 was independent of loading condition unlike extension for the other two fluids. This result seemed attributable to the low viscosity of L-CO2 and was consistent with previous observations for granite specimens that low-viscosity fluids like CO2 tend to induce widely extending cracks with many branches, with Mode II fractures being dominant. These features are more advantageous for shale gas production than those induced by injection of conventional slick water.

© 2015 by the Canadian Institute of Mining, Metallurgy & Petroleum and ISRM. It is often reported that the concept of single-plane-fracture is not sufficient to account for the productivity from shale gas/oil wells. Many researchers introduce the concept of the stimulated reservoir volume to describe observed production behaviour. However, the characteristics of the stimulated reservoir volume are not well understood. In this study, to investigate the characteristics of fractures and surrounding region induced by the hydraulic fracturing, a devised hydraulic fracturing experiment was conducted using the cylindrical shale specimens in the laboratory. Two resins were prepared as the fracturing fluid for the experiments: cyanoacrylate, an instant glue, mixed with a fluorescent paint (resin A), and methyl metaacrylate, a thermosetting acrylic resin, mixed with a fluorescent paint (resin B). These resins were able to fix within the specimen after fracturing. This is because the present study aimed to only detect fractures induced by hydraulic fracturing. Cut sections of the specimens were observed under ultraviolet light irradiation. It is expected that the hydraulically induced fractures and the surrounding regions will be detected because the induced fractures filled with the resin should emit light, while the other parts will not. The specimens, which were collected from the Kushiro Coal Mine in Hokkaido, Japan at the depth around 275 m, were roughly 85 mm in diameter, 170 mm in length, and cored normal to the sedimentary planes. An injection hole with a 10-mm diameter was drilled onto the center of the specimen parallel to the sedimentary plane to simulate hydraulic fracturing in shale gas development. The experiment was conducted under a uniaxial loading condition of 3 MPa and the fracturing fluid was injected into the sealed injection hole at a constant flow rate using a syringe pump. After the fracturing experiment, the resins were fixed in the specimens and then

Nurses play a critical role in delivering care to elderly people at primary health care level but there is no synthesis of research knowledge to guide community nursing practice in Japan. This review aims to identify nurse-led interventions that have been found to improve elder health at village level; the barriers and constraints that service providers face when delivering care to the elderly; and the experiences of elderly people and their caregivers. The electronic databases such as MEDLINE, CINAHL and Google Scholar were searched to retrieve peer-reviewed primary research literature. A narrative synthesis of the findings sections of the papers was applied to identify key themes. These themes are: socioculturally appropriate care; health improvements; barriers and constraints to care delivery and; experience of the elderly and families. Seven papers were included in the review. The synthesis identified that nurse-led health care for the elderly in rural Japan can be effective when it is targeted and culturally sensitive. The studies highlight a number of barriers to the provision of care. There is a need for further research to examine the issues affecting access to rural nursing care including health system factors, as well as the needs of the elderly and families themselves. Such studies will better inform the delivery of programs, reduce inequity and provide socio-culturally appropriate care to improve the well-being of the elderly.