In mature reservoirs, the success of preformed particle gel (PPG) treatment rests primarily on the ability of the PPG to reduce and/or plug the high permeable formations, but not damage the low permeable formations. Static test models (?ltration test model and pressure test model) were used to determine the effect of PPG on low permeable formations. This work used a strong preformed particle gel, Daqing (DQ) gel made by a Chinese company. The particle gel sizes were ranged from 30 to 120 mesh for this work. PPGs are sized in a millimeter or micrometer, which can absorb over a hundred times their weight in liquids. The gel strength was approximately 6500 Pa for a completely swollen PPG with 1 % (weight percentage) NaCl solution (brine). 0.05 %, 1 %, and 10 % NaCl solutions were used in experiments. Sandstone core permeability was measured before and after PPG treatments. The relationship between cumulative ?ltration volumes versus ?ltration times was determined. The results indicate that DQ gels of a particle size of 30–80 mesh did not damage the cores of a low permeability of 3–25 mD. The DQ gels of a smaller particle size ranging from 100 to 120 mesh damaged the core and a cake was formed on the core surface. The results also indicate that more damage occurred when a high load pressure (400 psi) was applied on the high permeability cores (290–310 mD). The penetration of the particle gels
into the low permeable formations can be decreased by the best selection of gel types, particle sizes, and brine concentrations.