Abstract The development of shale oil and gas resources has emerged as a pivotal trend in the global energy sector. Among the advanced reservoir stimulation techniques ,the injection of carbon dioxide (CO₂) has gained prominence for its potential to optimize fracturing treatment and enhance oil and gas recovery. This study investigates the effects of CO₂, slickwater, guar gum, and their composite fracturing fluids on the mechanical and fracture properties of bedding-developed shale and laminated shale. CO₂ alone reduces tensile strength the least, by 12.42% in bedding-developed shale and 29.38% in laminated shale, compared to slickwater and guar gum, which cause reductions of 42.21–45.63%. When combined with water-based fluids, CO₂ mitigates tensile strength reductions to 16.94–32.51%. CO₂ treatment reduces compressive strength by 28.84%, less than the 52.55% reduction caused by slickwater. Laminated shale treated with CO₂ and slickwater achieves higher fracture complexity, with a fractal dimension of 2.5. Fractal dimension analysis underscores the capacity of CO₂, both as a standalone treatment and in combination with guar gum, to enhance fracture complexity, with increases of 4–8.7% compared to water-based fracturing fluids. Fracture energy analysis demonstrates CO₂’s high energy efficiency, making it suitable for low-permeability reservoirs. A comprehensive evaluation indicates that CO₂ fracturing is optimal for bedding-developed shale, while laminated shale benefits more from CO₂ combined with slickwater. These findings offer valuable insights for optimizing fracturing designs in shale oil reservoirs, advancing the efficacy and sustainability of resource exploration technologies.
Suo et al. (Thu,) studied this question.