The effects of overburden stress on the specific storage and hydraulic conductivity of artesian aquifers

A mathematical algorithm is developed to determine the depth-dependent profiles of specific storage and hydraulic conductivity resulting from overburden stress in horizontally isotropic artesian aquifers. Vertical variations in the void ratio of the aquifer matrix brought about by overburden stresses determine the pore-volume compressibility and matrix permeability at specific depths within the aquifers which, in turn, determine the depth-dependent profiles of specific storage and hydraulic conductivity. Time-drawdown curves are obtained for two sands subjected to different overburden stresses. For shallow artesian aquifers with low overburden stress and high aquifer matrix compressibility, noticeable vertical gradients in specific storage occur. These vertical gradients cause deviations from the classical time-drawdown curves defined by the Theis solution. These deviations are negligible for deep artesian aquifers. ?? 1991.