13 research outputs found
Loading rate dependence of permeability evolution in porous aeolian sandstones
Mechanical properties of rocks are characterized by their notable dependence on the
applied deformation rate. However, little is known about the strain rate dependence of
fluid flow properties since most laboratory tests are conducted using a single, high strain
rate. We have investigated the effect of loading rate on the permeability of porous
sandstones by carrying out triaxial compression tests at four different temperatures and
strain rates with continuous monitoring of permeability, acoustic emission (AE), and pore
fluid chemistry. All tests are characterized by an initial permeability decrease due to
inferred compaction of favorably oriented cracks. The amount of initial permeability
reduction increases with decreasing strain rate, thus implying a more efficient initial
compaction at slower strain rates. At a later stage of loading, permeability correlates with
stress, ion concentration, or AE damage depending on the strain rate used. High strain rate
tests are characterized by a positive power law or logarithmic correlation between
permeability and AE damage. At slow strain rates, permeabilities decrease exponentially
with mean effective stress and axial strain for the Locharbriggs sandstone. The Clashach
sandstone exhibits a linear correlation between permeability and exit pore fluid
concentrations (Si, Mg, Fe, Al) if a slow strain rate is used. These observations have
important implications for the applicability of room temperature, high strain rate
laboratory data to the conditions that prevail in the Earth's crust