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Matrix acidizing is one of the most effective techniques to remove formation damage and increase the permeability of near well areas. However, the interaction of acid with crude oils produces acid sludge in some cases. This sludge is deposited on formations, blocks pores and flow paths, and reduces the productivity of wells. In this research, acid (HCl) compatibility tests at reservoir temperature (366.5° K), iron control test and emulsion test were performed along with sludge tests to optimize the acidizing fluid and prevent formation damage. The results show that the use of an anti-emulsion additive reduces the sludge formation by 28% because it prevents the formation of acid-oil emulsion. Moreover, increasing the concentration of HCl from 15 wt.% to 28 wt.% has caused a 23% increase in sludge formation. Finally, it can be said that the presence of ferric ions in acid has the largest role in the process of sludge formation because it caused a 211% increase in sludge weight.