Japan Geoscience Union Meeting 2018

Presentation information

[JJ] Oral

H (Human Geosciences) » H-SC Social Earth Sciences & Civil/Urban System Sciences

[H-SC05] CCUS (Carbon Dioxide Capture, Utilization, and Storage) for Climate Mitigation

Wed. May 23, 2018 10:45 AM - 12:15 PM 201B (2F International Conference Hall, Makuhari Messe)

convener:Masao Sorai(Institute for Geo-Resources and Environment, National Institute of Advanced Industrial Science and Technology), Ziqiu Xue(Research Institute of Innovative Tech for the Earth), Masaatsu Aichi(東京大学大学院新領域創成科学研究科), Chairperson:Sorai Masao(National Institute of Advanced Industrial Science and Technology)

11:00 AM - 11:15 AM

[HSC05-08] Saturation dependency of Bishop’s effective stress coefficient strongly affects strain behavior of rocks under two-phase flow condition

*Hiroki Goto1, Masaatsu Aichi2, Tomochika Tokunaga2 (1.National Institute of Advanced Industrial Science and Technology, 2.University of Tokyo)

Keywords:Bishop's effective stress coefficient, Two-phase flow, Deformation, Laboratory experiment, Numerical simulation

Understanding the strain behavior of rocks under two-phase flow condition is important to discuss a variety of subsurface processes including geological sequestration of carbon dioxide. Bishop’s effective stress coefficient (χ) is a parameter which defines “equivalent” fluid pressure in the stress-strain-fluid pressure relationships for porous media in two-phase fluid system (Coussy, 2007), and is commonly expressed as a function of the wetting-phase saturation. In this study, laboratory experiments and numerical simulations were conducted to investigate the effects of saturation dependency of χ on the strain behavior of rocks. In the experiment, compressed air was injected into a water-saturated cylindrical Berea sandstone sample from the bottom under hydrostatic external stress condition. During the experiment, confining pressure, air pressure at the bottom, and water pressure at the top were kept constant at 0.55, 0.35, 0.20 MPa, respectively, and axial and circumferential strains at half the height of the sample were monitored. Numerical simulation was conducted to reproduce the measured data by using a simulator which can solve coupled two-phase flow and deformation in porous media (Aichi, 2010). The measured strain behaviors before air breakthrough were reproduced well by assuming χ to be equal to water saturation, while those after the breakthrough was not. Non-linear relationships between χ and wetting-phase saturation explained both the measured strain behaviors before and after the breakthrough. It is concluded that saturation dependency of χ is an important parameter for understanding the strain behavior of rocks in two-phase fluid system.

Aichi, M. (2010), Thermodynamically consistent multiphase poroelasticity and its application to water-dissolved gas reservoir simulation, PhD thesis, Univ. of Tokyo.
Coussy, O. (2007), Revisiting the constitutive equations of unsaturated porous solids using a Lagrangian saturation concept, Int. J. Numer. Anal. Meth. Geomech., 31, 1675-1694.