Comparison of Prepared Hydrogels based on Chitosan by Heating and Irradiation Methods and Investigation of their Effects on Rheological Properties of Drilling Mud

Chitosan – Poly (N-isopropylacrylamide) hydrogels were synthesized by thermal and gamma irradiation methods. In the thermal method، initiators and crosslinkers were employed. It was found that the gamma irradiation method produced hydrogels of higher water swelling ratio. The hydrogels were used in drilling fluids and the important rheological properties of the muds such as apparent viscosity، plastic viscosity، and yield point as well as shear-shear rate diagrams were measured. Obtained results show that whereas linear polymer effects on mud properties are more significant in lower polymer concentrations، prepared crosslinked hydrogel effects are more significant at high concentrations. The hydrogel synthesized by gamma irradiation improved rheological properties of drilling fluids at higher concentrations of the hydrogel more effectively than the thermally produced hydrogel and linear polymers. It seems that addition of hydrogel to mud in powder form can increase the effects of rheological properties of drilling fluid. Thus، increase in gamma irradiation dose and monomer concentration، which rendered high swelling hydrogels، were more suitable for improving properties of drilling muds. In thermally synthesized hydrogels، increase in monomer and decrease in crosslinker concentration produced better hydrogels.