Experimental and numerical approach for fracture behaviors in circulation system.

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The extraction of geothermal energy from hot dry rocks is received by circulating fluid through fractures, as reservoirs, created by a hydraulic fracturing technique. In the design of reservoirs, fracture behavior study is needed to simulate the fluid behavior in circulation system under in-situ stress condition. Experimental and numerical approach of this paper are concerned with the circulation volume, the fracture aperture distribution and the fluid velocity distribution. Some laboratory and field experiments were conducted under various flow rate and stress condition. The variation of the inlet pressure under steady flow state was measured against the inlet flow rate. By the comparison of the flow rate on laboratory experiment and numerical calculation, the fracture under stress condition was obtained to keep some aperture, numerically about 0.5 mm in Inada granite (Fig. 16 and 17). Simulations of fluid behavior by coupled stress and flow analysis were carried out for 4 types of typical circulation models. The fluid velocity distribution and the fracture aperture distribution were obtained for each model type. By the comparison of coupled stress-flow analysis and only flow analysis for rigid fracture, the fluid behavior in circulation model was recognized to be influenced by the fracture aperture distribution under in-situ stress condition (Fig. 24 and 25).
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