Constructing high-performance water-blocking barriers at gas–water interfaces in gas reservoirs via interfacial spreading and in situ polymerization

Water intrusion in gas reservoirs with strong aquifer drives and pronounced heterogeneity presents significant challenges for production efficiency and cost control, as conventional rate management and drainage strategies often fail to address preferential water flow paths and trapped gas issues. Existing water shut-off technologies are constrained by poor agent transportability, imprecise placement, and neglect of the gas–water interface equilibrium. This study presents an advanced chemical water shut-off strategy that constructs large-area, crosslinked polymer water-blocking barriers directly at the gas–water interface within porous media through interfacial spreading-polymerization. The approach employs specific surfactants to enhance the spreading of an oil-phase monomer solution, thereby enabling broad interfacial coverage, while simultaneous in situ interfacial polymerization generates robust, crosslinked polymer networks. Specifically, the plugging system comprises two components: an oil solution and an aqueous solution. The oil solution contains cyclohexane, 0.1 wt% trimesoyl chloride (TMC), and the spreading agent octylphenol polyoxyethylene-4 (OP-4), which imparts strong spreading capacity to facilitate broad distribution of the TMC monomer. The aqueous solution comprises water, 2 wt% m-phenylenediamine (MPD), and sodium hydroxide. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Raman, and scanning electron microscopy (SEM) analyses confirm that the barrier is a highly cross-linked three-dimensional polyamide network with a highly dense internal structure and a thickness exceeding 300 µm, capable of effectively blocking pores, throats, and most natural fractures. Core flooding experiments further demonstrate that the barrier has substantial water-blocking performance, especially in low-permeability porous media.