Geology Reference
In-Depth Information
permeabilities is important for disposal of radioactive waste and in harnessing
geothermal energy. An increase in temperature will cause a volumetric
expansion of the rock material leading to reduction in fracture aperture and
an overall decrease in rock permeability. Studies at Stripa mine in Sweden
demonstrated a reduction in permeability of granites by a factor of three
when temperature was increased by 25°C by circulating warm water.
METHODS OF AQUIFER PARAMETER ESTIMATION
Hydraulic properties of an aquifer can be estimated in laboratory and in the
field. However, values obtained in the laboratory from rock samples are not
representative of the formation.
Table 2 gives a list of commonly used field methods. The choice of a
particular method depends on the purpose of study. For small scale problems,
as in geotechnical investigation, seepage of water to mines and tunnels and
contaminant transport, packer tests, slug tests and tracer tests are preferred.
Cross-hole pneumatic injection tests are recommended for detailed
investigation on a local scale (Illman and Neuman, 2003). For estimation of
aquifer parameters and groundwater development and management on a
regional scale, pumping test method should be used.
Table 2:
Field test methods for the estimation of hydraulic
characteristics of hard rock aquifers
Purpose of
Size of area under
Distribution of
Test Method
Investigation
Investigation
Fractures
A few km
2
Geo-technical
Random
Packer (Lugeon) test,
investigations; mine
slug test, tracer
drainage; waste
injection test
Systematic
Modified packer test,
fractures of
cross-hole hydraulic
1, 2 or 3 sets
test; tracer injection
> 100 km
2
Groundwater
Random and
Pumping test
development; water
closely
A few km
2
Geothermal and
Random
Well interference test,
petroleum reservoirs
tracer injection test
In hard rocks, as the geometry of the fractures will greatly influence the
flow characteristics and pumping test data, structural analysis is significant
in the planning of pumping tests and interpretation of test data. Reader may
refer to Kruseman and deRidder (1990), Singhal and Gupta (1999) and
Lloyd (1999) for a detailed account of the pumping tests and interpretation
of data. The effect of scale of measurement on permeability values is depicted
in Fig. 6.
