Diffusion in the Matrix of Granitic Rock Field Test in the Stripa Mine Part 2.

1983 ◽  
Vol 26 ◽  
Author(s):  
Lars Birgersson ◽  
Ivars Neretnieks
Keyword(s):  
Laboratory Experiments ◽  
Granitic Rock ◽  
Nuclear Waste Repository ◽  
Rock Matrix ◽  
Injection Hole ◽  
Undisturbed Rock ◽  
Natural Stress ◽  
The Matrix ◽  
Migration Experiment ◽  
Stress Environment

ABSTRACTA migration experiment in the rock matrix is presented. The experiment has been carried out in “undisturbed” rock, that is in rock under its natural stress environment. Since the experiment was performed at the 360 m-level (in the Stripa mine), the rock was subject to nearly the same conditions as the rock surrounding a nuclear waste repository as proposed in the Swedish concept (KBS).The results show that all three tracers (Cr-EDTA, Uranine and 1-) have passed the zone disturbed by the presence of the injection hole and migrated some distance into “undisturbed” rock.These results indicate the existence of a connected micro fissure system in undisturbed rock, in which tracers (and therefore radionuclides) can migrate. Diffusivities obtained in this experiment are comparable to those obtained in laboratory experiments.

Diffusion in the Matrix of Granitic Rock Field Test in the Stripa Mine

1987 ◽  
Vol 112 ◽  
Author(s):  
Lars Birgersson ◽  
Ivars Neretnieks
Keyword(s):  
Granitic Rock ◽  
Nuclear Waste Repository ◽  
Filling Material ◽  
Rock Matrix ◽  
In Situ Experiment ◽  
Undisturbed Rock ◽  
Disturbed Zone ◽  
The Matrix ◽  
Stress Environment

AbstractThree similar migration experiments in the matrix of granitic rock are presented. The experiments have been carried out in “undisturbed” rock, that is rock under its natural stress environment. Since the experiments were performed at the 360 m level (in the Stripa Mine), the rock was subjected to nearly the same conditions as the rock surrounding a nuclear waste repository as proposed in the Swedish concept (SKB).A mixture of three non-sorbing (conservative) tracers, Uranine, Cr-EDTA and I−, were injected into the granitic rock matrix for time periods of months up to years. The subsequent overcorings of the injection holes showed that the tracers had in some cases migrated at least ≈ 400 mm (measuring limit) into the rock matrix for the experiment with the longest injection time. It could also be seen that there were large differences in migration distance into the rock matrix for samples taken fairly close to each other. One example where the tracers have diffused through fissure coating (filling) material located in “undisturbed” rock is also presented.The results from all three experiments show that all three tracers have migrated through the disturbed zone close to the injection hole, through the fissure coating material and a distance into the “undisturbed” rock matrix.These results therefore indicate that dissolved compounds may migrate into the rock matrix. This migration into the rock matrix will increase the area available for sorption of radionuclides significantly and may therefore increase the migration times for radionuclides by order(s) of magnitude.Diffusivities and hydraulic conductivities obtained in this in-situ experiment compare well with those obtained in laboratory experiments.

Diffusion in the Matrix of Granitic Rock. Field Test in the Stripa Mine

1981 ◽  
Vol 11 ◽  
Author(s):  
Lars Birgersson ◽  
Ivars Neretnieks
Keyword(s):  
Field Test ◽  
Granitic Rock ◽  
Pore System ◽  
Undisturbed Rock ◽  
The Matrix ◽  
Migration Experiment

A migration experiment with the objective to investigate the existence of a connected pore system in undisturbed rock has been performed in the Stripa mine at the 360 m-level.

Channeling and its Potential Consequences for Radionuclides Transport

1987 ◽  
Vol 112 ◽  
Author(s):  
Luis Moreno ◽  
Ivars Neretnieks
Keyword(s):  
Water Flow ◽  
Granitic Rock ◽  
Flow Distribution ◽  
Crystalline Rock ◽  
Fractured Media ◽  
Radionuclide Transport ◽  
Rock Matrix ◽  
Sorption Coefficient ◽  
The Matrix ◽  
Large Flow

SummaryRadionuclide transport through fractured media is usually calculated assuming that water flows in most of the fractures. Several observations in the field and the laboratory show that flow is very unevenly distributed in fractured crystalline rock. These observations indicate that most of the water flow takes place in a limited number of channels. The channels are seldom wider than a few meters and are often much narrower. This means that the surface of the fracture in contact with the flowing water (wetted surface) is less than one might expect.This low value of the wet surface of the fracture may considerably influence the transport of radionuclides through fractured media. If the channels do not intersect over a certain distance, then the channels may be modelled as a bundle of independent channels. Channels with a large flow and small sorption surface will carry the tracer rapidly and in large amounts.Calculations are performed for cases where channeling is assumed to take place. The most important entities to assess are the water flow distribution in the different channels, the wetted surface of the channels, the diffusivity into the rock matrix, and the sorption coefficient in the matrix. Experimental data for the water flow distribution are used and the transport of nuclides is calculated for the different channels. From these values the concentration of the effluent is determined. The results show that the retardation for the nonsorbing nuclides is negligible. Retardation is only important for the nuclides which are strongly sorbed on the granitic rock. Calculations are also done assuming other channel frequencies and other overall water flowrates.

Allocation of fracturing intervals and justification of fracture parameters in the pre-Jurassic deposits

2021 ◽  
pp. 9-19
Author(s):  
P. A. Boronin ◽  
N. V. Gilmanova ◽  
N. Yu. Moskalenko
Keyword(s):  
Permeability Coefficient ◽  
Complex Structure ◽  
High Flow ◽  
Well Testing ◽  
Rock Matrix ◽  
Unconventional Reservoir ◽  
Flow Rates ◽  
Matrix Permeability ◽  
The Matrix ◽  
Standard Set

The object of research in this article is the productive deposits of the pre-Jurassic complex. The pre-Jurassic complex is of great interest, this is an unconventional reservoir with a complex structure and developed fractured zones. High flow rates cannot be determined by the rock matrix, since the matrix permeability coefficient is on average 2−3 md. In this regard, there is the problem of separation of fractured intervals according to a standard set of well testing.

Diffusion in the Matrix of Granitic Rock: Field Test in the Stripa Mine

1990 ◽  
Vol 26 (11) ◽  
pp. 2833-2842 ◽  
Author(s):  
Lars Birgersson ◽  
Ivars Neretnieks
Keyword(s):  
Field Test ◽  
Granitic Rock ◽  
The Matrix

Radionuclide Migration: Laboratory Experiments with Isolated Fractures

1981 ◽  
Vol 6 ◽  
Author(s):  
R. S. Rundberg ◽  
J. L. Thompson ◽  
S. Maestas
Keyword(s):  
Laboratory Experiments ◽  
Field Experiments ◽  
National Laboratory ◽  
Test Site ◽  
Matrix Diffusion ◽  
Fracture Flow ◽  
Flow Equations ◽  
Welded Tuff ◽  
The Matrix ◽  
Element Migration

ABSTRACTLaboratory experiments examining flow and element migration in rocks containing isolated fractures have been initiated at the Los Alamos National Laboratory. Techniques are being developed to establish simple fracture flow systems which are appropriate to models using analytical solutions to the matrix diffusion - flow equations, such as those of I. Neretnieks [1]. These experiments are intended to be intermediate steps toward larger scale field experiments where it may become more difficult to establish and control the parameters important to nuclide migration in fractured media.Laboratory experiments have been run on fractures ranging in size from 1 to 20 cm in length. The hydraulic flow in these fractures was studied to provide the effective apertures. The flows established in these fracture systems are similar to those in the granite fracture flow experiments of Witherspoon et al. [2]. Traced solutions containing 85Sr and 137Cs were flowed through fractures in Climax Stock granite and welded tuff (Bullfrog and Tram members, Yucca Mountain, Nevada Test Site). The results of the elutions through granite agree with the matrix diffusion calculations based on independent measurements of Kd. The results of the elutions through tuff, however, agree only if the Kd values used in the calculations are lower than the Kd values measured using a batch technique. This trend has been previously observed in chromatographic column experiments with tuff.

Comparison of alternative approaches to modelling gas migration through a higher strength rock

2012 ◽  
Vol 76 (8) ◽  
pp. 3319-3326 ◽  
Author(s):  
A. R. Hoch ◽  
M. James
Keyword(s):  
Host Rock ◽  
Fractured Rock ◽  
Gas Migration ◽  
Rock Matrix ◽  
Nuclear Decommissioning ◽  
The Matrix ◽  
Safety Case ◽  
Alternative Approaches ◽  
The Uk ◽  
Strength Rock

AbstractThe Radioactive Waste Management Directorate of the UK Nuclear Decommissioning Authority has prepared a generic disposal system safety case (DSSC) that covers a range of possible host rock environments. In many of the waste packages considered in the DSSC, the formation of gases by chemical and microbial processes is likely to occur. In order to demonstrate safety, it is necessary to understand the rates at which the gases are generated and their subsequent migration from a disposal facility after closure. This paper is concerned with modelling gas migration through a fractured higher strength host rock. A first set of simulations compares alternative approaches to modelling gas migration through a fractured rock. The approaches differ in their representation of the interaction between the fractures and the rock matrix. As expected, the gross features of many of the simulations are very similar, with a single continuum approach in which the porosity is set equal to either the fracture porosity or the matrix porosity providing the bounding cases. Gas migration is slower for those simulations where the gas can access more of the rock matrix. A final simulation, with a heterogeneous permeability field, is compared with the other simulations, again showing a very similar evolution.

scholarly journals Permeability of matrix-fracture systems under mechanical loading – constraints from laboratory experiments and 3-D numerical modelling

2019 ◽  
Vol 49 ◽  
pp. 95-104 ◽  
Author(s):  
Guido Blöcher ◽  
Christian Kluge ◽  
Harald Milsch ◽  
Mauro Cacace ◽  
Antoine B. Jacquey ◽  
...  
Keyword(s):  
Inelastic Deformation ◽  
Laboratory Experiments ◽  
Elastic Behaviour ◽  
Fracture System ◽  
Parallel Plates ◽  
Stress Strain ◽  
Cubic Law ◽  
Matrix Fracture ◽  
The Matrix ◽  
Fracture Domain

Abstract. The permeability of single fractures is commonly approximated by the cubic law assumption, which is however only valid under the condition of a single phase laminar flow between parallel plates. Departure from cubic law are related to many features like aperture fluctuations due to fracture surface roughness, relative shear displacement, the amount of flow exchange between the matrix and the fracture itself, etc. In order to quantify constitutive relationships among the aforementioned aspects, we have conducted a flow-through experiment with a porous rock sample (Flechtinger sandstone) containing a single macroscopic fracture. Based on this experiment, we obtained range of variations of intrinsic rock parameters, permeability and stress-strain relationships of the combined matrix-fracture system under hydrostatic loading. From the measured deformation of the matrix-fracture system, we derived the evolution in the mechanical aperture of the fracture. In order to quantify the processes behind the laboratory observations, we carried out coupled hydro-mechanical simulations of the matrix-fracture system. Navier–Stokes flow was solved in the 3-dimensional open rough fracture domain, and back-coupled to the Darcy flow and the poroelastic behaviour of the rock matrix. The results demonstrate that the elastic behaviour and the related permeability alteration of the fracture domain could be captured by the numerical simulation. Furthermore, the stress-strain values obtained in the vicinity of the fracture asperities suggest that inelastic deformation develops at low mechanical load. An attempt was made to quantify the inelastic deformation by using the failure envelope obtained by laboratory experiments (whether tensile, shear, compaction, or a combination of those). However, change in permeability observed in the experiments are significantly larger than that in the simulation showing the importance of plastic deformation during opening and closure of the fracture and its impact on the cubic law approximation.

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