In this study, investigation of permeability reduction due to formation damage by invaded drilling fluids of sandstone-based, lime-containing core plugs from the southeastern region of Turkey were studied. The tests were performed by using dynamic filtration set-up that was constructed at the laboratory. In the experiments, nine core plugs of 7 cm length and 3.81 cm (1.5 in) diameter were used. Three different drilling fluid types using two different polymers were prepared and tests were made at three different filtration pressures. The direct effect of filtration pressure on fines migration was studied. The filtration properties and the thicknesses of the filter cakes were measured. It was observed that permeability of the sandstone samples reduced due to circulation of the drilling fluid and the filter cake thickness increased with increasing differential well bore pressure.