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DEM-SJM combined 2D-hydraulic fracturing simulation for consideration of the influence of differential stressGold Open Access

Authors: H. Ohtani, H. Mikada and J. Takekawa
Event name: The 22nd International Symposium on Recent Advances in Exploration Geophysics (RAEG 2018)
Session: Geoexploration
Publication date: 24 May 2018
DOI: 10.3997/2352-8265.20140228
Language: English
Info: Extended abstract, PDF ( 969.33Kb )

Summary:
For improving the production of conventional oil and shale gas, the practice of hydraulic fracturing has been increasing in recent years. In addition, hydraulic fracturing is used for the development of geothermal energy known as hot dry rock (HDR) geothermal power, and enhanced geothermal system (EGS), and for measuring the rock failure strength and the orientation of principal stress direction, etc. On the other hand, hydraulic fracturing has some environmental impact, such as pollution caused by chemical substances in injected proppant or fluid, induced seismicity, etc. Since it is necessary to minimize the environmental impact, techniques to predict propagating directions and distances of fractures to be generated hydraulically, which are known still very difficult, have been waited for. In this paper, we demonstrate the influence of differential stress and the anisotropy using numerical experiments based on distinct element method (DEM) combined with smooth joint model (SJM). Hydraulic fractures in general propagate in the direction of maximum principal stress on large differential stress conditions. As the differential stress decreased, the propagating directions hydraulic fractures curves to the direction of bedding plane, i.e., anisotropic direction of weak rock strength, and sometimes fractures branch to plural directions. These results suggest that the behavior and propagating direction of hydraulic fractures are strongly influenced by both the differential stress and the rock strength anisotropy in the underground shallow layer. 

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