A free-radical inverse emulsion polymerization formulation has been developed for preparation of acrylamide (AAm)/sodium 2-acrylamido-2-methylpropanesulfonate (AMPSNa)/N-vinylpyrrolidone (VP) terpolymers. An aqueous solution of a blend of monomers is emulsified in n-decane using Tween 85 (Tw85). Ammonium persulfate (APS) and dicumyl peroxide (DCP) were used as initiators for water and oil phases, respectively. The reactions were catalyzed by temperature and by a redox pair; the former is achieved at 60 degrees C and the latter by adding tetramethylethylenediamine (TEMED) and sodium bisulphite (BisNa) to activate the initiator in water and oil phase, respectively. The emulsion type, stability, conversion, and rate of polymerization were analyzed. The obtained terpolymer was characterized by elemental analysis, infrared spectroscopy (FTIR), C-13 nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), gel permeation chromatography (GPC), and rheology. Thermal catalyzed emulsion polymerization initiated with DCP showed the best performance as viscosity control agent and as polymeric precursor for in situ gel forming, for water mobility control and flow diversification, respectively. Both application for enhanced oil recovery purposes in harsh oil reservoir conditions are presented. (C) 2017 Society of Plastics Engineers