Field Tests - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 497

Figure 15.28 Orientation of test holes for Lugeon tests in a rock mass with two orthogonal
discontinuity sets D1 and D2 (Wittke 1990)
The interpretation of Lugeon tests based on laminar, steady state, radial fl ow is econom-
ically only possible in rock masses with permeability coeffi cients of >10 -8 m/s. Lugeon
tests in rock formations with lower permeability therefore require long-term tests. As an
example, in a long-term test conducted in rock salt over one year, a permeability coeffi -
cient of some 10 -13 m/s was determined (Durup 1993).
15.8.2 Other Methods of Permeability Testing
Injection and production tests
The test duration of packer tests can be considerably reduced when the test results ob-
tained during the transient fl ow phase are interpreted. Particularly for low permeability
rock, different packer test procedures have been developed which are based on the eval-
uation of the transient fl ow phase with respect to permeability (Stormont et al. 1991,
Miehe et al. 1993, Hekel 1994, Wittke 1999, Wittke 2000a). These tests generally can
be subdivided into injection tests and production tests. In an injection test, a test fl uid
such as water, brine, oil or gas is injected into the rock mass. In a production test, water
is withdrawn from the rock mass by pumping or seeping of water into the test section.
When a fl uid other than water is used as the injection fl uid, the results of hydraulic tests
are normally expressed in terms of the so-called “intrinsic permeability” K, which is
independent of the test fl uid. K and the water permeability coeffi cient k are related as
follows:
(15.42)