Development of an Electrostatically Anchored Three-Dimensional Cross-Linked Gel System for Water-Channeling Control in Reservoirs with Severe Water Channeling

Severe water channeling caused by long-term water flooding has become a major obstacle to the efficient development of mature offshore reservoirs. Conventional gel systems can provide profile control and water shutoff to some extent; however, their plugging strength and long-term stability are often insufficient under severe channeling conditions. In this work, an electrostatically anchored three-dimensional (3D) cross-linked gel system was developed for reservoirs with severe water channeling. The design was based on the interfacial characteristics of dominant water-channeling pathways, where prolonged water scouring renders the rock surface strongly water-wet and negatively charged. A cationic cross-linker was introduced to adsorb onto the pore surface through electrostatic attraction, thereby modifying the interfacial properties, and then cross-linked with the injected polymer to form a 3D gel network in situ. The cross-linking and plugging mechanisms were investigated by zeta potential analysis, particle size measurement, scanning electron microscopy, and molecular dynamics simulation. Its enhanced oil recovery performance was evaluated by core flooding experiments. The results showed that the developed system could strongly interact with negatively charged rock surfaces, increase flow resistance, and form a spatially interconnected gel network with a positively charged surface. This electrostatically anchored structure enhanced gel retention and plugging stability in severe water-channeling pathways. Under target reservoir conditions, the developed system provided a substantially higher oil recovery than both water flooding and a conventional gel system. These findings demonstrate the strong potential of the developed gel system for water-channeling control and enhanced oil recovery in Bohai reservoirs and other similar mature oilfields.