The Jiyang Depression has abundant shale oil resources, and elastic development is the main way to utilize shale oil. As the pore pressure decreases, the bedding fractures, sand filled fractures, and pores undergo deformation under compression, leading to a decrease in permeability/conductivity, which affects the permeability and development effectiveness of shale. Based on the liquid pressure pulse experiment, the variation law of the permeability of shale containing bedding fractures in elastic development was clarified, supplemented by online CT displacement testing, to study the changes in the morphology and quantity of bedding fractures in fracturing elastic development. Experimental studies have shown that the permeability of shale with bedding fractures decreases exponentially and linearly with the increase of effective stress. There is a clear turning point in the exponential decrease, and the closure pressure is around 30 MPa, indicating strong stress sensitivity; The linearly decreasing core exhibits moderate to strong stress sensitivity; After secondary loading pressure, the permeability of the core decreases irreversibly. The permeability of the core decreases approximately linearly with the increase of effective stress, and the stress sensitivity of the core becomes moderately weak; During the process of hydraulic fracturing and pressure increase, the volume of bedding fractures increases, while during the process of elastic pressure failure, the volume of bedding fractures decreases. However, the magnitude of change is smaller than that of the pressure increase process, and the stress sensitivity is relatively weak. The study innovatively utilized liquid pressure pulse stress sensitivity experiments combined with CT scanning technology to clarify the stress sensitivity of shale bedding fractures and visually display them, providing technical support for achieving large-scale development of shale oil.

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Experimental Study on Shale Microfracture Flow Based on Stress Sensitivity

  • Ting Chen,
  • Chun-lei Yu,
  • Zhi-gang Sun,
  • Min Zhang,
  • Qiang Sun

摘要

The Jiyang Depression has abundant shale oil resources, and elastic development is the main way to utilize shale oil. As the pore pressure decreases, the bedding fractures, sand filled fractures, and pores undergo deformation under compression, leading to a decrease in permeability/conductivity, which affects the permeability and development effectiveness of shale. Based on the liquid pressure pulse experiment, the variation law of the permeability of shale containing bedding fractures in elastic development was clarified, supplemented by online CT displacement testing, to study the changes in the morphology and quantity of bedding fractures in fracturing elastic development. Experimental studies have shown that the permeability of shale with bedding fractures decreases exponentially and linearly with the increase of effective stress. There is a clear turning point in the exponential decrease, and the closure pressure is around 30 MPa, indicating strong stress sensitivity; The linearly decreasing core exhibits moderate to strong stress sensitivity; After secondary loading pressure, the permeability of the core decreases irreversibly. The permeability of the core decreases approximately linearly with the increase of effective stress, and the stress sensitivity of the core becomes moderately weak; During the process of hydraulic fracturing and pressure increase, the volume of bedding fractures increases, while during the process of elastic pressure failure, the volume of bedding fractures decreases. However, the magnitude of change is smaller than that of the pressure increase process, and the stress sensitivity is relatively weak. The study innovatively utilized liquid pressure pulse stress sensitivity experiments combined with CT scanning technology to clarify the stress sensitivity of shale bedding fractures and visually display them, providing technical support for achieving large-scale development of shale oil.