Modified Siloxane Supercritical CO₂ Fracturing Fluid Thickener for Shale Reservoirs: Optimized Synthesis, Low Dissolution Pressure, Significant Thickening and Proppant Carrying Capability, Filter Loss Resistance

Aiming at the problems of weak proppant carrying capacity and serious filtration loss caused by the extremely low viscosity (0.02–0.06 mPa·s) of supercritical carbon dioxide fracturing fluid, a modified silicone-based thickener was designed and synthesized, and its thickening mechanism was explored. First, the conditions of the hydrosilylation reaction were optimized using response surface methodology. The successful introduction of thickening and solubilizing groups was verified by Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance spectroscopy (1H NMR). Second, the solubilization and thickening properties of multisystem polymer thickeners were investigated by using a self-designed high-temperature and high-pressure visual reactor: the viscosity of carbon dioxide could be increased to 4.308 mPa·s at a content of 5 wt % of thickener, and the proppant-carrying capacity (1.04 cm/s) and filtration-loss-resistant (0.343 m/min0.5) of supercritical carbon dioxide fracturing fluids were significantly improved by the addition of thickener (DHTAF). Finally, the dissolution and thickening mechanism of the thickener in CO2 was investigated by electrostatic potential distribution, cohesive energy density (CED), and interaction energy (Eint) using molecular simulation. The above research can provide an effective reference for the efficient exploitation of shale reservoirs and the application of supercritical CO2. It not only helps to solve the current problems in the field of supercritical carbon dioxide fracturing but also has far-reaching implications for promoting the technological progress of shale gas exploitation and the sustainable development of the energy industry.