Research on the method to improve the efficiency of ScCO2 fracturing and the mechanism of proppant transport and drag-reducing

Supercritical carbon dioxide (ScCO2) fracturing still faces two major technical challenges: poor proppant-carrying performance and high flow resistance. This study proposes a novel approach to designing CO2 fracturing fluid additives by combining quantum chemistry simulations with molecular dynamics simulations. Using this method, a new additive was successfully synthesized. The additive effectively carries proppants and reduces pipeline friction, offering multifunctional benefits. Unlike most CO2 thickening agents, this additive not only exhibits excellent thickening performance but also utilizes elasticity to enhance its proppant-carrying capability. The flexible stacking and potential slippage regions between its layers impart elasticity, while the three-dimensional network structure significantly improves its proppant-carrying capacity. Furthermore, the layered structure can adsorb onto pipe walls to form a surface film, thereby reducing turbulence generation. Laboratory tests indicate that adding 3 wt% of this additive increases the viscosity of the CO2 system by approximately 10 times. At 20 MPa and 60 °C, it reduces pipeline friction by 38.3 % and decreases the settling velocity of proppants in ScCO2 by about 50 %. Additionally, it effectively mitigates proppant agglomeration. From an environmental perspective, the additive causes minimal damage to rock formations, with a damage rate of only 11.62 %.