Development of a gel-based temporary blocking agent: tuning activation temperature, degradability, and integrated pressure-resistance assessment using a dynamic simulation

Workover operations frequently require temporary wellbore isolation to control formation fluid inflow; however, conventional lost-circulation materials and mechanical isolation assemblies often exhibit limited sealing efficiency, poor post-treatment removability, or severe formation damage potential. An integrated laboratory-scale wellbore simulation framework was developed to systematically evaluate Temporary Plugging Agent (TPA) gel-plug (GP) performance by integrating precursor injectivity, apparent activation temperature, static gel strength, confined differential pressure resistance, geometric confinement effects (H/D ratio), contaminant sensitivity, acid-triggered degradation behavior, and formation-damage potential. Two distinct synthesis pathways were investigated: (1) in-situ free-radical copolymerization of acrylamide (ACM) monomer using polyethylene glycol diacrylate (PEGDA) as a difunctional crosslinker with thermal persulfate initiators, and (2) ex-situ chemical post-crosslinking of linear polyacrylamide (PAM) using hexamethylenetetramine (HMTA). Ten distinct formulations were prepared and systematically evaluated. While ex-situ formulations failed to establish mechanically stable, self-supporting gel networks, in-situ formulations yielded robust three-dimensional covalently crosslinked hydrogel networks. The optimized in-situ formulation displayed excellent injectivity with a pre-gel viscosity below 5 cP (25 °C) and a tunable activation temperature ranging from 54 °C to 63 °C depending on the persulfate initiator used. Dynamic tube pressure assessments demonstrated a maximum differential pressure resistance of 1,410 psi. Contamination with sodium chloride (NaCl), potassium chloride (KCl), and crude oil reduced pressure resistance by 31%, 18%, and 14%, respectively. Controlled degradation assessments demonstrated a 78% mass reduction within 30 days in 20 wt% hydrochloric acid (HCl), while post-degradation core-flooding tests showed a 3.50% permeability reduction under the conditions of this study (96.5% permeability recovery ratio). The developed in-situ gel plug system successfully combines high precursor injectivity, substantial pressure-bearing capability, controlled chemical removability, and minimal formation damage, making it a promising temporary isolation technology for severe fluid-loss and workover applications.