This paper deals with mechanical damage linked to stress and deformation changes associated with drilling and well completion operations and associated permeability changes. Irreversible or plastic deformations caused by pore collapse and particle rearrangement result in permanent fabric alterations due to induced anisotropy. Permeability changes are linked to damage state, anisotropic damage, dilation and stress state changes. Molecular dynamics simulations using disc assemblages and laboratory triaxial test experiments on weakly cemented sandstones clearly indicates that the induced anisotropy and deformation due to shearing significantly alters the permeability; and also its value depends on the direction in which it is measured. Severe anisotropy in permeability is the result of local heterogeneity due to damage. The molecular dynamics simulation is shown to be a powerful tool to generate insights into the physical processes of particulate behavior. The paper illustrates the implications of induced anisotropy effects on formation damage.

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