Synchrotron 3D microtomography of halite aggregates during experimental pressure solution creep and evolution of the permeability

Pressure solution creep is one of the possible processes of mechano-chemical deformation that controls porosity and permeability variations in the upper crust. The three-dimensional geometry of the porous network of halite aggregates was imaged during compaction driven by pressure solution creep using X-ray synchrotron computed microtomography. This technique can be used to monitor individual grain contacts and whole aggregate textural changes during deformation. By reconstructing subvolumes, the 3D porosity of the aggregates was extracted. The time-resolved decrease in permeability during porosity reduction was calculated by solving the Stokes equations. The permeability remained isotropic and decreased from 2.1 to 0.15 Darcy after 18.2% compaction. Two microscopic mechanisms can explain the permeability reduction: grain indentation and pore connectivity reduction by precipitation on the free surface of pore throats.