A Comprehensive Experimental Investigation on Stress Response Behavior of Organic-Rich Shale Fracture Permeability

The stress-dependent fracture permeability plays a vital role in shale reservoir drilling and hydrocarbon production process. An undesired change of fracture permeability under varying effective stress can induce serious safe and financial problems, such as lost circulation and production decline. Despite being a hot focus, the stress-dependent fracture permeability of shale is still not well understood, especially the impact factor. In this paper, two organic-rich shales in China are collected to conduct measurement of shale permeability at varying effective stress. The effect of effective stress change path, effective stress change method, shale type, fracture type and fluid immersion are on stress response behavior of shale fracture permeability is discussed. The results show that fracture permeability of shale decreases with the increasing effective stress and the varying tendency fits the logarithm model well. A deviate reference point from in situ stress leads an inaccurate stress sensitivity evaluation. Fracture permeability stress sensitivity of confining pressure varying method is stronger than pore pressure varying method. Fracture permeability of Chang 7 shale is more stress sensitive than Longmaxi shale. Artificial fracture has the strongest permeability stress sensitivity and the propped fracture has the weakest one. The fluid immersion increases the fracture permeability stress sensitivity.