Japan Geoscience Union Meeting 2019

Presentation information

[J] Oral

S (Solid Earth Sciences ) » S-CG Complex & General

[S-CG61] Dynamics in mobile belts

Tue. May 28, 2019 9:00 AM - 10:30 AM Convention Hall A (2F)

convener:Yukitoshi Fukahata(Disaster Prevention Research Institute, Kyoto University), Toru Takeshita(Department of Natural History Sciences, Graduate School of Science, Hokkaido University), Hikaru Iwamori(Geochemical Evolution Research Program, Japan Agency for Marine-Earth Science and Technology), Chairperson:Keisuke Yoshida(東北大学大学院理学研究科 地球物理学専攻), Masaoki Uno(東北大学)

9:30 AM - 9:45 AM

[SCG61-15] Fluid-Flow, Resistivity and Elastic Wave Velocity Simulation of Digital Rock Fracture and Comparison with Experimental Data

*Kazuki Sawayama1, Fei Jiang2, Takuya ISHIBASHI3, Takeshi Tsuji4, Yasuhiro Fujimitsu4 (1.Department of Earth Resources Engineering, Graduate school of engineering, Kyushu University, 2.Department of Mechanical Engineering, Faculty of Engineering, Yamaguchi University, 3.Fukushima Renewable Energy Institute, National Institute of Advanced Industrial Science and Technology, 4.Department of Earth Resources Engineering, Faculty of engineering, Kyushu University)

Keywords:digital rock physics, elastic wave velocity, resistivity, fracture flow, Lattice Boltzmann Method

Fluid-flow in the fracture plays a key role to evaluate the mechanism of earthquake and fractured reservoirs (e.g., geothermal and shale) since fracture flow constrains the fluid-flow behavior and rock strength under the ground. To predict the fluid-flow and its distribution under the ground, geophysical explorations (seismic and electromagnetic methods) have been broadly applied. However, there is no established rock physical model to estimate the fluid-flow properties (e.g., permeability) in the fracture from resistivity or elastic wave velocity, and thereby fluid-flow behavior in the fracture are difficult to be precisely interpreted by geophysical explorations. For the better interpretation of these exploration data, more detailed investigation about the effect of fluid-flow behavior on resistivity and elastic wave velocity of fractured rocks is required. In this study, in order to discuss this effect, we measured and calculated them by using fractured rock samples which have different apertures.

We conducted laboratory fluid-flow testby using fractured Inada granite (50 mm in a diameter, 80 mm in a length) which have single tensile fracture with different aperture. For the numerical model, we digitalized this real rock fracture (0.1 mm grid resolution) to calculate fluid-flow, resistivity and elastic wave velocity under the same condition with experiment. Three dimensional fracture flow was simulated by using Lattice Boltzmann Method and we applied Finite Element Analysis to calculate resistivity and elastic wave velocity after this fluid-flow simulation.

As a result, permeability decreases with pressure increase under laboratory experiment and calculated permeability also shows the decrease as the aperture increases. This agreement suggests that fracture permeability is constrained by aperture closure due to the pressure effect. From the permeability matching approach, we found that permeability dramatically decreases after the fracture contact area exceeds ~80%. At this threshold value, fluid-flow path, resistivity and elastic wave velocity show inflections. Our results suggest that permeability change caused by aperture closure could be estimated by seismic and electromagnetic explorations.