Stress induced permeability anisotropy of Resedimented Boston Blue Clay

In Resedimented Boston Blue Clay (RBBC), a low‐plasticity glacio‐marine illitic mudrock, the ratio of the horizontal to vertical permeability (the permeability anisotropy, rk) increases from 1.2 to 1.9 as the porosity decreases from 0.5 to 0.37 and the permeability decreases by more than 1 order of magnitude. Backscattered Scanning Electron Microscope (BSEM) images taken at formation stress levels reveal that particles rotate perpendicular to the axial loading direction by ∼22°, with larger particles rotating more significantly and achieving more uniform alignment than smaller particles. We show experimentally that preferred platy particle orientation can explain our permeability anisotropy measurements. The permeability anisotropy of mechanically compressed mudrocks is minimal,