How does impairment occur?
As water is injected into the disposal zone, the formation tends to act as a filter and traps any suspended solids being carried along with the water. These materials will accumulate, building a filter cake causing increasingly greater resistance to flow. Suspended solids can include formation fines (i.e., clays, silts and sands coming from producing wells), corrosion or scale products, microbiological residues from bacterial growth, entrained paraffin solids, oxidative residues from contact with air, or a variety of other substances. Suspended oil can film out onto formation surfaces, increasing the drag of the water flowing past. Under turbulent conditions, oil and water can combine within the formation to generate viscous emulsions. Changes in temperature and pressure can destabilize water chemistry, causing scale precipitates to form. Actively growing bacteria can colonize the formation, producing large quantities of byproducts. The result of each of these processes is that pressur
