The experimental investigating in water-rock interaction to reduce the thermal cracking threshold temperature of organic-rich shale

Thermal stimulation has excellent potential for enhancing the productivity of organic-rich shale. However, this shale's high thermal cracking threshold temperature (Ttct) results in excessive energy consumption and stringent casing safety requirements. Thus, optimizing thermal stimulation technology and reducing the Ttct is critical for efficient oil and gas production. This study proposes a novel method for quantifying the Ttct by fitting the Sshaped characteristics of the curve using the Sweibull2 model and defining the temperature corresponding to the maximum first-order derivative as the threshold value. Furthermore, we investigate the feasibility of reducing the high Ttct via water-rock interactions. Our findings show that the average Ttct of the anhydrous shale rock samples was 574 degrees C, which decreased significantly to 344 degrees C and 336 degrees C for those samples saturated with distilled water and KCl solution, respectively. Persulfate oxidation resulted in noticeable reductions in the shale's Ttct and led to sample deformation and the initiation of large-scale fractures at temperatures below 200 degrees C. However, the Ttct did not decrease significantly after acidizing and averaged 545 degrees C. In summary, by adjusting the salinity of the fracturing fluid and incorporating suitable additives to match the reservoir's properties, the effectiveness of heat treatment can be significantly enhanced. These findings present potential opportunities for improving oil and gas recovery while simultaneously reducing the energy consumption associated with thermal stimulation.