Experimental study on permeability enhancement of tight sandstone by hydraulic fracturing under the true tri-axial system

Hydraulic fracturing plays a crucial role in extracting natural gas from tight sandstones. Temperature and in-situ stress significantly influence the effectiveness of fracturing. However, the mechanisms through which these parameters enhance reservoir permeability require further investigation. We executed hydraulic fracturing and seepage experiments on tight sandstones across varying temperatures, analyzed the variation of injection pressure during the fracturing process, and compared permeability changes before and after fracturing. Our findings indicate that as the temperature rises, the breakdown pressure of the specimen decreases, with a maximum reduction of ∼26.15%, and existing theoretical models can estimate the breakdown pressure range. The specimen permeability before and after fracturing exhibited exponential decline with increased axial stress. However, the formation of penetrating fractures notably enhanced the specimen permeability after fracturing, surpassing before-fracturing levels. To quantify the impact of hydraulic fracturing on permeability, we introduced a permeability improvement coefficient, which peaked at around 15.7. This coefficient decreased as axial stress increased, with higher temperatures associated with more significant reductions. The insights from this study can guide hydraulic fracturing construction.