Chitosan/Polyacrylamide Green Gels for Water Control in High-Temperature Reservoirs

Abstract

The rheology of a gel system composed of polyacrylamide (PAM) and chitosan is studied under typical reservoir conditions. The impacts of the degree of chitosan deacetylation, temperature, and salinity on the gelation behavior are assessed. The said system was prepared under ambient conditions and matured for 24 h at altered temperatures ranging from 50 up to 125 °C. An optimum formulation has been identified considering the rheological response and the initial viscosity constraints. The increase in the degree of syneresis with the degree of deacetylation indicates the long-term thermal stability of the gels. Ammonium chloride was an effective retarder for the PAM/chitosan gelant, which delayed the gelation time from 60 to 210 min when 2 wt % is used; however, it compromised the final gel strength. The chitosan/PAM system showed a good rheological behavior and potential as a green plugging agent in high-temperature oil and gas wells. Chitosan could be an alternative for commercial crosslinkers, such as polyethyleneimine.