This study aims to determine the field and petrographic properties of sandstones observed in Arsuz-İskenderun (Hatay) region and micro-size porosity changes in acidizing stages. The fine-grained sandstones of the Aktepe formation have more quartz grains than the other components and the binding material is matrix. Rock fragments that consist of fossil shells, limestone and igneous fragments are observed relatively to quartz and feldspar grains in the Kızıldere formation sandstones. The first step of reservoir rock acidizing is HCl acidizing and the process is experimentally provided by capillarity experiment. HCl with dilution rates of 7.5% - 15% - 30% was absorbed into the samples at room temperature and after 100 minutes, effective distances were observed as 0.6-0.8-1.1 cm and dissolved rock amounts as 32.82-34.02-35.54 g, respectively. In acidizing process, the average porosity analysed with Micro-CT is 39.6% of acidified samples with 15% diluted acid and non-acidified samples, equivalent results were obtained with porosity values measured by well logs. There is an increase in the porosity of about 16% with acidizing. Pores were bonded together by acidizing and pore size increase about 20%. The change in the pore throat by acidizing is 105%. Calculation of porosity of rocks by Micro-CT and image processing methods can be performed faster compared to the other methods.