Ionic transport in swelling shale

A model of hindered transport of solute in shale is described, and then used to predict the radial flow of water and solute away from a wellbore. Shale strata in the field may be assumed to extend to infinity, but laboratory tests are performed using finite samples of shale; both cases are studied. Osmotic effects can create transient changes in the pore pressure (and total stress) which may lead to a disintegration of the drilled shale and mechanical instability of the wellbore.