This study discusses formation damage mechanisms that were caused by commonly used chemical treatments. The chemicals used in these treatments included a scale inhibitor a biocide-corrosion inhibitor an in situ gelled acid, a full-strength mud acid, and a. mutual solvent. These treatments were designed to remove a known form of formation damage. However they created new forms of formation damage, which resulted in a significant decline in the performance of the treated wells. Case histories that illustrate the initial and new formation damage mechanisms are explained in detail. Laboratory and field studies that were performed to identify these mechanisms are discussed. Moreover this paper highlights the remedial actions and field application that resulted in restoring the performance of various wells without affecting the integrity of the formation (both carbonate and sandstone). Finally, recommendations are given to minimize formation damage due to various chemical treatments.