• Geophysics and Geophysical Exploration
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• v.7 no.1
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• pp.25-32
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• 2004

We have carried out laboratory measurements of P-wave velocity and deformation strain during $CO_2$ injection into a porous sandstone sample, in dry and water-saturated conditions. The rock sample was cylindrical, with the axis normal to the bedding plane, and fluid injection was performed from one end. Using a piezoelectric transducer array system, we mapped fluid movement during injection of distilled water into dry sandstone, and of gaseous, liquid, and supercritical $CO_2$ into a water-saturated sample. The velocity changes caused by water injection ranged from $5.61\;to\;7.52\%$. The velocity changes caused by $CO_2$ injection are typically about $-6\%$, and about $-10\%$ for injection of supercritical $CO_2$, Such changes in velocity show that the seismic method may be useful in mapping $CO_2$ movement in the subsurface. Strain normal to the bedding plane was greater than strain parallel to the bedding plane during $CO_2$ injection; injection of supercritical $CO_2$ showed a particularly strong effect. Strain changes suggest the possibility of monitoring rock mass deformation by using borehole tiltmeters at geological sequestration sites. We also found differences associated with $CO_2$ phases in velocity and strain changes during injection.

• Tunnel and Underground Space
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• v.10 no.3
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• pp.387-394
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• 2000

This is study investigates the changes of subsidence and hydraulic conductivity by underground mining Coupling between post-mining induced strains and strain-dependent hydraulic conductivities is obtained by idealizing a jointed rock mass as an equivalent porous medium in which the hydraulic conductivity of a single joint is defined through parallel plate description. Results indicate that post-mining hydraulic conductivities are directly related to the strain field occurred by subsidence induced deformation. Maximum subsidence and hydraulic conductivity values increase as a panel width does widen. Joint spacing has an effect on the intensity of the changes in hydraulic conductivity.

• Proceedings of the Korean Nuclear Society Conference
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• 2001.05a
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• pp.361.2-361
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• 2001

• Proceedings of the Korean Nuclear Society Conference
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• 2001.10a
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• pp.276.1-276
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• 2001

• Geomechanics and Engineering
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• v.9 no.1
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• pp.15-24
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• 2015

The porosity is often regarded as a linear function of fluid pressure in porous media and permeability is approximately looked as constants. However, for some scenarios such as unconsolidated sand beds, abnormal high pressured oil formation or large deformation of porous media for pore pressure dropped greatly, the change in porosity is not a linear function of fluid pressure in porous media, and permeability can't keep a constant yet. This paper mainly deals with the relationship between the damage variable and permeability properties of a deforming media, which can be considered as an exploratory attempt in this field.

• Geomechanics and Engineering
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• v.23 no.4
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• pp.327-338
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• 2020

The role of precise prediction of subsurface fluids and discrimination among them cannot be ignored in reservoir characterization and petroleum prospecting. A suitable rock physics model should be build for the extraction of valuable information form seismic data. The main intent of current work is to present a rock physics model to analyze the characteristics of seismic wave propagating through a cracked porous rock saturated by a three phase fluid. Furthermore, the influence on wave characteristics due to variation in saturation of water, oil and gas were also analyzed for oil and water as wet cases. With this approach the objective to explore wave attenuation and dispersion due to wave induce fluid flow (WIFF) at seismic and sub-seismic frequencies can be precisely achieved. We accomplished our proposed approach by using BISQ equations and by applying appropriate boundary conditions to incorporate heterogeneity due to saturation of three immiscible fluids forming a layered system. To authenticate the proposed methodology, we compared our results with White's mesoscopic theory and with the results obtained by using Biot's poroelastic relations. The outcomes reveals that, at low frequencies seismic wave characteristics are in good agreement with White's mesoscopic theory, however a slight increase in attenuation at seismic frequencies is because of the squirt flow. Moreover, our work crop up as a practical tool for the development of rock physical theories with the intention to identify and estimate properties of different fluids from seismic data.

• Tunnel and Underground Space
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• v.13 no.1
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• pp.20-32
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• 2003

To understand the behavior of migration of contaminants in a fractured porous medium is a key to assure the overall safety of a potential radwaste repository. The feasible retention mechanism of contaminant transport in a tinctured medium are sorption of contaminants on solid surface and matrix diffusion of contaminants from a fracture into an adjacent porous medium. The acceleration mechanisms are the migration of contaminants in the form of pseudo-colloids and the limit of a volume f3r matrix diffusion. In this paper, the effects of these two acceleration mechanisms are studied mathematically, then semi-analytically computed by the application of the Talbot theorem and verified. Results indicate that the acceleration processes cannot be neglected in the modeling of contaminant transport in a fractured porous medium.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.4 no.1
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• pp.9-15
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• 2006

For the accurate safety assessment of potential radioactive waste disposal site which is located in the crystalline rock it is important to simulate the mass transportation through engineered and natural barrier system precisely, characterized by porous and fractured media respectively. In this work the methods to construct discrete fracture network for the analysis of flow and mass transport through fractured-porous medium are described. The probability density function is adopted in generating fracture properties for the realistic representation of real fractured rock. In order to investigate the intersection between a porous and a fractured medium described by a 2 dimensional rectangular and a cuboid grid respectively, an additional imaginary fracture is adopted at the face of a porous medium intersected by a fracture. In order to construct large scale flow paths an effective method to find interconnected fractures and algorithms of swift detecting connectivities between fractures or porous medium and fractures are proposed. These methods are expected to contribute to the development of numerical program for the simulation of radioactive nuclide transport through fractured-porous medium from radioactive waste disposal site.

• Nuclear Engineering and Technology
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• v.26 no.4
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• pp.453-460
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• 1994

The migration equation is modified for a three-member decay chain in the fracture and porous matrix Analytical solutions are obtained by utilizing Laplace transform the initial conditions of Delta function and Bateman equation. The concentrations for each nuclide of Np$^{237}$ -U$^{233}$ -Th$^{229}$ and U$^{234}$ -Th$^{230}$ -Ra$^{226}$ chains selected from the 4n＋1 and 4n＋2 chains are plotted by utilizing analytical solutions in the fracture. Retardation coefficient of the nuclides are obtained using those of the granite. The results indicate that the daughter nuclides such as U$^{233}$ , Th$^{229}$ , Th$^{230}$ and Ra$^{226}$ become important at the far field from the repository though there is very small initial inventory in the waste solid or spent fuel, for they are produced by the mother nuclides decayed in the fracture and porous matrix.

• Nuclear Engineering and Technology
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• v.34 no.3
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• pp.218-231
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• 2002

Using a three-dimensional numerical code, B3R developed for nuclide transport of an arbitrary length of decay chain in the buffer between the canister and adjacent rock in a high- level radioactive waste repository by adopting a finite difference method utilizing the control- volume scheme, some illustrative calculations have been done. A linear sorption isotherm, nuclide transport due to diffusion in the buffer and the rock matrix, and advection and dispersion along thin rigid parallel fractures existing in a saturated porous rock matrix as well as diffusion through the fracture wall into the matrix is assumed. In such kind of repository, buffer and rock matrix are known to be important physico-chemical harriers in nuclide retardation. To show effects of buffer and rock matrix on nuclide transport in HLW repository and also to demonstrate usefulness of B3R, several cases of breakthrough curves as well as three- dimensional plots of concentration isopleths associated with these two barriers are introduced for a typical case of decay chain of $^{234}$ Ulongrightarrow$^{230}$ Thlongrightarrow$^{226}$ Ra, which is the most important chain as far as the human environment is concerned.