Polymer gel system has been identified as having the potential for blocking and diverting water flow. However, the current polymer reported an inability to maintain its mechanical strength, limited penetration depth, and instability in reservoir conditions of high temperature and high pressure. A distinctive bentonite nanomer clay (PGV)/acrylamide (AM)-co-2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) preformed particle gel with poly(ethylene glycol-b-tetramethylene oxide) (PEGTMO) coating to control the swelling kinetics is formulated. The in-house formulated gel�s ability to block and divert water flow in a porous medium is studied. The formation recipe of the gel was achieved by numerous swelling tests as induced by brine solution under reservoir conditions. Through the swelling tests, the long-term thermal stability of the gel solution was demonstrated. The incorporation of PGV clay particles improves the swelling and mechanical properties of the gel. Premature swelling can be avoided with PEGTMO coating as it slows the swelling rate over a 10-minute period, which gives the advantage of controlling the swelling before reaching the intended site of action during coreflood experiments. The rheological behavior of the hydrogel features rubber-like mechanical behavior with a viscosity value of 1.17 cp, which displayed water-like characteristics. Further, significant permeability reduction of large fractures is demonstrated by the coreflooding experiment with a calculated result of 96.2. This formulated gel could offer the solution as a blocking agent in void space channels containing reservoirs that leads to a reduction of water cut due to thief zones. Copyright © 2023 Society of Petroleum Engineers.