Fracture closure in pure quartz sandstone at low stress and temperature

The purpose of this paper is to report on the outcome of a continuous long-term flow-through experiment
conducted on a fractured pure quartz sandstone (Fontainebleau) at 60 ◦C. Changes in effective pressure (1, 17,
and 29 MPa) and pore fluid composition (deionized water and Si-rich solution) were sequentially imposed to
investigate their respective effect on time-dependent fracture closure. Hydraulic fracture aperture, as derived
from permeability measurements, showed to decrease substantially by about 50% within the 120 days of the
experiment. Based on complementary analyses of the effluent Si concentration and microstructural in-
vestigations, it is suggested that, mechanistically, pressure solution, stress corrosion cracking, and free face
dissolution contribute to the overall aperture decrease. However, as the fracture morphology evolves with time,
the deformation mechanisms that are driven by diffusion and/or stress (i.e., pressure solution and stress
corrosion cracking) may deactivate, yielding a significant decrease in the fracture closure rate. The study sug-
gests follow-up experiments to quantitatively decipher the relative importance of the complex and coupled
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processes affecting fracture aperture and permeability.