Diagenetically altered sandstones ("shaly sands") are extremely susceptible to formation damage during drilling, completion, stimulation, or enhanced-recovery operations. This susceptibility arises because of the development of diagenetic minerals within the pore system and because of physical and chemical interactions between the diagenetic minerals and the injected fluids.

Formation-damage mechanisms can be separated into three groups: mechanical, chemical, and physical. The mechanical mechanisms include migrating clays, swelling clays, and sloughing clays. The chemical mechanisms include dissolution of minerals and precipitation of minerals. Physical mechanisms of formation include emulsion blockages or water blockages.

The scanning electron microscope allows the geologist or engineer to observe directly the mechanisms for formation damage in a reservoir and to design his treatment accordingly. The SEM can also be used to observe the effects of well treatments and evaluate their success or failure.

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