Self-Diverting Emulsified Polymer System for Selective Gelation in Water Zones

Excess water production is one of the major challenges in mature oil fields, driving up operational costs and creating significant environmental concerns. Although both mechanical and chemical methods have been applied, a universally reliable and long lasting solution that consistently mitigates excess water without compromising oil production has not yet been established.The work covers laboratory formulation and rheological evaluation, focusing on gelation times of various formulations. The primary objective is to develop and assess a novel emulsified polymer-cross-linker system for selective water shutoff, specifically designed to remain stable and pumpable in oil-rich zones while rapidly gelling upon contact with water. The emulsified system was formulated using an acrylamide-based copolymer, polyethyleneimine cross-linker, and a surfactant emulsifier, with soda ash incorporated for pH adjustment and gelation control in both water and oil systems. Rheological tests were conducted on an Anton Paar MCR-302 rheometer under a constant confining pressure of 500 psi and varying temperatures to simulate reservoir conditions. Gelation experiments were conducted systematically varying cross-linker concentration, soda ash content, and temperature (25 °C to 94 °C) to evaluate gelation kinetics and fluid stability. By integrating rheological measurements with compositional adjustments, the study quantified how formulation parameters influence gelation onset, viscosity evolution, and phase stability in oil- and water-based environments. At 35 vol% polymer and 5 vol% cross-linker, the emulsion demonstrated pronounced phase selectivity. In crude oil, viscosity remained near 80 cP with no observable gelation for more than 550 minutes, whereas in de-ionized water rapid gelation began at about 140 minutes and viscosity exceeded 2000 cP. Gelation time shortened markedly with increasing cross-linker concentration and temperature, while soda ash acted as a retarder by delaying gelation and lowering the initial viscosity to enhance injectivity. Aging tests showed syneresis at higher cross-linker loadings, evidenced by gel shrinkage and a discernible color shift, indicating the need to optimize formulation for long-term stability. Overall, the rheology data confirm that the emulsion can be injected without mechanical zonal isolation, selectively plugging water-bearing intervals while leaving oil-rich zones largely unaffected, providing a tunable and thermally robust approach to chemical water management. This study advances the design of responsive emulsified polymer systems for conformance control. Unlike conventional gels that block both oil and water, the proposed formulation achieves water-specific gelation through phase-selective behavior, eliminating the need for zonal isolation. Emulsifiers and retarders enable gelation tuning, while the emulsion's diversion capability allows effective bull-heading without coiled tubing. By self-directing into water-bearing zones and selectively forming a gel, the system offers a practical, cost-effective solution to extend well life, reduce water-handling costs, and enhance sustainability in high water-cut reservoirs.