Ideally, a well stimulation activities is to increase production by improving such the flow of hydrocarbons from the drainage area into the well bore, however, however in one field in Southern of Oman, the acidizing created a trend of H2S increase. The common preliminary quick check usually will be based on the review of stimulation fluid characteristics whether carrying any sulphide or H2S and giving an impact to the wells. Some lesson learned in Oman is the water supply sources during the job always content H2S. The level of H2S after acidizing showed an alarming increase with time, casting doubts on future integrity assurance across the processing facility. As the materials used in the X and down stream receiving facilities are not to be NACE 175 souring compliant and consider H2S released are hazard for safety (HSE). The production chemistry and reservoir study have initiated an integrated H2S Monitoring and implemented a Mitigation Program by improving H2S onsite measurement and method revision and established proper well surveillance. As a result, the investigated the cause of souring show a positive SRB Bacteria and the acidizing cause a flash of H2S from Iron Sulfide scale as a product from bacteria populations. Overall its improved business performance, HSE awareness and saving the plant upgrade cost.