In the present study, we used Kalamkas, which is a typical Kazakhstani oilfield, which produces wastewater with high Ca²⁺/Mg²⁺ and Fe²⁺ concentrations, as a case study. We investigated a method for preparing Fe²⁺ polymer solutions without oxygen isolation under the conditions of salinity >110 × 10³ mg/L, Ca²⁺/Mg²⁺ concentration >7000 mg/L, and Fe²⁺ concentration >30 mg/L. Fe²⁺-resistant groups were grafted onto the molecular chains of a hydrophobically associating polymer prepared using existing synthesis technology to overcome the decrease in apparent viscosity of the polymer solution due to the oxidation of Fe²⁺ during solution preparation. The experiments showed that PAM-IR with iron-resistant groups can be completely dissolved in the wastewater within 180 min, and can tolerate an NaCl concentration of up to 0.23 × 10⁶ mg/L, a Ca²⁺ concentration of up to 10 × 10³ mg/L, an Mg²⁺ concentration of up to 9 × 10³ mg/L, and a Fe²⁺ concentration of up to 90 mg/L, with favorable thickening performance and resistances to NaCl, Ca²⁺, Mg²⁺, and Fe²⁺. PAM-IR has good injection performance and can establish a high resistance factor (F_R) and residual resistance factor (F_RR) to increase the sweep efficiency. Therefore, it is potentially useful for enhancing oil recovery.