Hydraulic fracturing operations have been widely used to enhance reservoir permeability during the extraction of oil, shale gas and tight sandstone gas. Recently, non-aqueous fracturing fluids, such as supercritical carbon dioxide and nitrogen, have been proposed as the potential fracturing fluid candidates due to their advantages of decreasing formation damage, conserving water resources and avoiding injection-induced seismicity. However, the breakdown process of the non-aqueous fracturing process and the breakdown mechanism remain mysteries. In this research, we report a series of hydraulic fracturing experiments with low-permeable shale samples and high-permeable sandstone samples by water, supercritical carbon dioxide, and nitrogen gas under different injection rates. Moreover, we use a coupled fluid-rock interaction model to visualize the distribution of fluid pressure near the injection borehole during hydraulic fracturing before the sample breakdown. The results indicate that the fluid infiltration decreases the breakdown pressure by increasing the pore pressure and decreasing the effective stress, especially for high-permeable sandstone rock and low-viscosity fracturing fluid. Also, breakdown pressure increases with increasing fluid injection rate, and the conventional Hubbert-Willis and Haimson-Fairhust equations can still effectively determine the upper and lower limits in predicting the breakdown pressure. Our results suggest that lower viscosity fluid with a lower injection rate leads to a lower breakdown pressure, which is suitable to be implemented for the reservoirs with high intrinsic permeability.

水力压裂作业已广泛用于提高石油，页岩气和致密砂岩气开采过程中的储层渗透率。近来，已经提出非水压裂液，例如超临界二氧化碳和氮气，作为潜在的压裂液候选物，因为它们具有减少地层破坏，节约水资源和避免注入引起的地震活动的优点。然而，非水压裂过程的破裂过程和破裂机理仍然是个谜。在这项研究中，我们报告了在不同注入速率下，水，超临界二氧化碳和氮气对低渗透性页岩样品和高渗透性砂岩样品进行的一系列水力压裂实验。而且，我们使用耦合的流体-岩石相互作用模型来可视化在样品破裂之前在水力压裂过程中注入井附近的流体压力分布。结果表明，流体渗透通过增加孔隙压力和降低有效应力而降低了破裂压力，特别是对于高渗透性砂岩和低粘度压裂液而言。而且，击穿压力随着流体注入速率的增加而增加，并且常规的Hubbert-Willis和Haimson-Fairhust方程仍可以有效地确定预测击穿压力的上限和下限。我们的结果表明，具有较低注入速率的较低粘度流体会导致较低的破裂压力，这适用于具有高固有渗透率的储层。