Research and application of self-suspending proppants based on block copolymer modification in coalbed methane wells

Conventional proppants exhibit limited sand-carrying capacity and incomplete gel breaking below 60 °C, resulting in inadequate fracture support and reduced stimulated reservoir volume. In this study, a self-suspending, high-salinity-resistant block copolymer was synthesized by precisely controlling the copolymer composition and topology. Based on this, a novel self-suspending proppant fracturing fluid system was developed. Its sand-carrying capacity, gel-breaking behavior, friction reduction, salt resistance, and transport performance were systematically evaluated and compared with those of emulsion polymer-based fracturing fluids. The self-suspending proppant achieved complete dispersion within 45 s and maintained suspension stability for over 25 h. It supported sand loadings up to 60%, and a small amount of proppant could carry more than ten times its weight in quartz sand. The friction reduction rate exceeded 71%, averaging 2.32% higher than that of emulsion polymer systems. The self-suspending fluid demonstrated minimal proppant settling during transport, resulting in improved placement and fracture conductivity. In contrast, emulsion polymer-based systems suffered from poor dispersion, emulsion formation, and reduced viscosity and transport distance. Field trials in the Linxing coalbed methane reservoir showed that a mixture of 10% self-suspending proppant with 26% conventional quartz sand enabled stable injection and doubled gas production compared to wells treated with emulsion polymer-based fluids. These results demonstrate the feasibility and efficiency of self-suspending proppant-based fracturing fluids for use in coalbed and shale reservoirs.