Methods include introducing a multistage treatment fluid into one or more intervals of a wellbore, wherein the treatment fluid contains one or more stages of a polymer-forming composition and one or more stages of a spacer fluid and initiating polymerization of the one or more stages of polymer-forming composition. Methods may include designing a multistage treatment fluid containing one or more stages of a polymer-forming composition and one or more stages of a spacer fluid, wherein or more stages of the polymer-forming composition comprises a thermosetting polymer; and pumping the multistage treatment fluid into a wellbore, wherein the pumping rate is determined by constructing a model based upon (a) the minimum pumping rate determined from the critical reaction temperature and the downhole temperature, (b) the fracture closing time, (c) the temperature within one or more fractures, and (d) the maximum pumping rate.