  In low-permeability porous media, the velocity of a fluid flow exhibits a
nonlinear dependence on the imposed pressure gradient. This non-Darcian flow
behavior has important implications to geological disposal of nuclear waste,
hydrocarbon extraction from shale, and flow and transport in clay-rich
aquifers. Temperature has been postulated to affect the threshold pressure
gradient of a non-Darcian flow; however, the supporting data is very limited.
In this study we for the first time report a systematic measurement of the
threshold pressure gradient under various permeabilities and temperatures. The
results show that a higher temperature leads to a lower threshold pressure
gradient under the same permeability and a faster reduction of the threshold
pressure gradient with increasing permeability. The experimental data are
fitted to a two-parameter model to determine the parameters, h0 and a, which
characterize the interfacial fluid-solid interactions and the transition
between the Darcy and non-Darcian regimes.
