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POSIVA Report 1997-13

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Name:

Through-Diffusion, Permeability, Channel-Flow and In Situ Results for Porosity and Migration Properties of Rock Samples by He-Gas Methods

Writer:

Kari Hartikainen; Juhani Hartikainen; Jussi Timonen

Language:

English

Page count:

45

ISBN:

951-652-038-3; 1239-3096

Summary:

Working report: POSIVA-raportti POSIVA-97-13, 43 sivua
ISBN 951-652-038-3


THROUGH-DIFFUSION, PERMEABILITY, CHANNEL-FLOW AND IN SITU
RESULTS FOR POROSITY AND MIGRATION PROPERTIES OF ROCK
SAMPLES BY He-GAS METHODS


ABSTRACT

Rock samples from three candidate sites for nuclear waste repositories at Olkiluoto,
Kivetty and Romuvaara were analysed by He-gas methods, and their porosities,
diffusivities and permeabilities were determined.
The through-diffusion method was used to determine the porosities and effective
diffusion coefficients of the short drill-core samples, and the permeability method to
measure their permeability coefficients. The channel-flow method was used to
determine the products of porosity and effective diffusion coefficient for the long drill-
core samples. The matrix porosities and effective diffusion coefficients determined are
for helium in samples saturated with nitrogen gas. The measured through-diffusion
porosities varied between 0.03 and 2.20 %, and the effective diffusion coefficients of
helium in samples saturated by nitrogen gas between 3.20´10-10 and 1.30´10-8 m2/s. The
measured permeability coefficients varied between 4.65´10-21 and 8.97´10-19 m2. The
products of porosity and effective diffusion coefficient measured by the channel-flow
method varied between 4.0´10-16 and 2.7´10-13 m2/s.
The results of the channel-flow measurements were in each case smaller than the
corresponding results obtained from the through-diffusion measurements. There was a
close correspondence between the effective diffusion coefficients and permeability
coefficients. Three series of drill-core samples were measured by the helium-gas
through-diffusion and permeability methods in order to determine the effect of sawing
and sample length on the porosity and migration properties of rock samples. The
measured porosities varied between 0.03 and 0.25 %, the effective diffusion coefficients
of helium in samples saturated by nitrogen gas between 2.50´10-10 and 9.00´10-9 m2/s
and the permeability coefficients between 3.29´10-21 and 2.95´10-19 m2.
The measured porosities, and diffusion and permeability coefficients indicate that
sawing seems to have a very small effect on the measured rock characteristics in pure
migmatitic mica gneiss samples. Correspondingly, it seems to have a minor effect in
mica gneiss and granite samples. On the other hand, in granodiorite samples sawing
seems to affect the characteristics. In situ measurements were repeated for two of the six
drill holes in the TVO Research Tunnel at Olkiluoto, and the effect of bedrock rest
humidity on the migration properties was analysed. Channel-flow measurements were
also made on five long drill-core samples from these six drill holes, and through-
diffusion measurements on six short pieces of these samples, in order to compare the
results of all three methods. The measured porosities varied in the range from 0.04 to
0.15 %, the effective diffusion coefficients of helium in samples saturated by nitrogen
gas from 4.50´10-11 to 2.00´10-9 m2/s and their products from 1.80´10-14 to 3.00´10-12
m2/s (through-diffusion), from 2.2´10-15 to 2.0´10-12 m2/s (channel flow) and from
1.0´10-14 (8.0´10-16 measured in 1996) to 8.0´10-13 m2/s (in situ).
The results determined show that the products of porosity and effective diffusion
coefficient are on the average fairly similar for all methods. Different methods for same
sections of drill holes produce results that appreciably differ only in few cases. The in
situ results measured in 1995 and 1996 for drill hole VLJ-KR15 (depth 125-195 cm)
differed by a factor 25. This deviation could not be explained. The above mentioned
samples and holes were not exactly from the same sections, however, and there may also
be some differences in the characteristics of the measured samples. The effect of
bedrock rest humidity was observed to be negligible on the measured migration
properties if the so-called mixture ratio, which describes the level of humidity of the
outflowing gases in the measurements, was under 10 g/kg.

Keywords: He-gas method, porosity, effective diffusion coefficient, permeability
coefficient, bedrock rest humidity


POSIVA-raportti POSIVA-97-13, 43 sivua
ISBN 951-652-038-3


THROUGH-DIFFUSION, PERMEABILITY, CHANNEL-FLOW AND IN SITU
RESULTS FOR POROSITY AND MIGRATION PROPERTIES OF ROCK
SAMPLES BY He-GAS METHODS


ABSTRACT

Rock samples from three candidate sites for nuclear waste repositories at Olkiluoto,
Kivetty and Romuvaara were analysed by He-gas methods, and their porosities,
diffusivities and permeabilities were determined.
The through-diffusion method was used to determine the porosities and effective
diffusion coefficients of the short drill-core samples, and the permeability method to
measure their permeability coefficients. The channel-flow method was used to
determine the products of porosity and effective diffusion coefficient for the long drill-
core samples. The matrix porosities and effective diffusion coefficients determined are
for helium in samples saturated with nitrogen gas. The measured through-diffusion
porosities varied between 0.03 and 2.20 %, and the effective diffusion coefficients of
helium in samples saturated by nitrogen gas between 3.20´10-10 and 1.30´10-8 m2/s. The
measured permeability coefficients varied between 4.65´10-21 and 8.97´10-19 m2. The
products of porosity and effective diffusion coefficient measured by the channel-flow
method varied between 4.0´10-16 and 2.7´10-13 m2/s.
The results of the channel-flow measurements were in each case smaller than the
corresponding results obtained from the through-diffusion measurements. There was a
close correspondence between the effective diffusion coefficients and permeability
coefficients. Three series of drill-core samples were measured by the helium-gas
through-diffusion and permeability methods in order to determine the effect of sawing
and sample length on the porosity and migration properties of rock samples. The
measured porosities varied between 0.03 and 0.25 %, the effective diffusion coefficients
of helium in samples saturated by nitrogen gas between 2.50´10-10 and 9.00´10-9 m2/s
and the permeability coefficients between 3.29´10-21 and 2.95´10-19 m2.
The measured porosities, and diffusion and permeability coefficients indicate that
sawing seems to have a very small effect on the measured rock characteristics in pure
migmatitic mica gneiss samples. Correspondingly, it seems to have a minor effect in
mica gneiss and granite samples. On the other hand, in granodiorite samples sawing
seems to affect the characteristics. In situ measurements were repeated for two of the six
drill holes in the TVO Research Tunnel at Olkiluoto, and the effect of bedrock rest
humidity on the migration properties was analysed. Channel-flow measurements were
also made on five long drill-core samples from these six drill holes, and through-
diffusion measurements on six short pieces of these samples, in order to compare the
results of all three methods. The measured porosities varied in the range from 0.04 to
0.15 %, the effective diffusion coefficients of helium in samples saturated by nitrogen
gas from 4.50´10-11 to 2.00´10-9 m2/s and their products from 1.80´10-14 to 3.00´10-12
m2/s (through-diffusion), from 2.2´10-15 to 2.0´10-12 m2/s (channel flow) and from
1.0´10-14 (8.0´10-16 measured in 1996) to 8.0´10-13 m2/s (in situ).
The results determined show that the products of porosity and effective diffusion
coefficient are on the average fairly similar for all methods. Different methods for same
sections of drill holes produce results that appreciably differ only in few cases. The in
situ results measured in 1995 and 1996 for drill hole VLJ-KR15 (depth 125-195 cm)
differed by a factor 25. This deviation could not be explained. The above mentioned
samples and holes were not exactly from the same sections, however, and there may also
be some differences in the characteristics of the measured samples. The effect of
bedrock rest humidity was observed to be negligible on the measured migration
properties if the so-called mixture ratio, which describes the level of humidity of the
outflowing gases in the measurements, was under 10 g/kg.

Keywords: He-gas method, porosity, effective diffusion coefficient, permeability
coefficient, bedrock rest humidity


Keywords:

He-gas method; porosity; effective diffusion coefficient; permeability coefficient; bedrock rest humidity

File(s):

Through-Diffusion, Permeability, Channel-Flow and In Situ Results for Porosity and Migration Properties of Rock Samples by He-Gas Methods (pdf) (751.2 KB)


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