Study on the Mechanical Damage Characteristics of Gulong Shale Oil with Different Types of Fracturing Fluids

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.