Carboxymethyl cellulose (CMC) based materials have been proposed as preformed particle gels (PPGs) for reducing excessive water production in oil and gas reservoirs. Multi-sized dry particles ranging between 100 and 1180 μm have been synthesized using microwave-assisted grafting copolymerization of CMC and acrylamide (AM)/n,n''-methylene-bisacrylamide (MBA). FTIR and SEM confirmed CMC crosslinked polyacrylamide's chemical structure and morphology (CMC/CPAM). Thermo-gravimetric analysis has demonstrated the thermal stability of dry PPGs up to 309 °C. CMC/CPAM showed slightly high absorbency in brine 2 (TDS = 67.3 g/L) compared to brine 1 (TDS = 33.65 g/L), 1% NaCl, and deionized water, with swelling ratios (SR) between 7.1 and 12.9 g/g at room temperature regulated by MBA weight ratio. The effect of particle size, pH, temperature, and aging on SR and mechanical strength was investigated and discussed based on the CMC/CPAM structures. The swollen PPGs showed excellent resistance to temperatures up to 100 °C with a storage modulus of 9 kPa. The particle size was estimated based on salinity, pH, and temperature and controlled between 118 μm and 3 mm at high temperature (100 °C) and high salinity (TDS = 67.3 g/L) conditions to match the need for carbonate reservoirs. Core flooding experiments demonstrated the effective plugging efficiency of the PPG in open fracture models.