Oil and gas are main storage resources in the pores and fractures of rocks. Under a complex stress environment, the permeability evolution of the reservoir rock fracture directly affects the flow of oil and gas, which is important in oil and gas exploration and development. The permeability test of a single sample in complex stress paths was performed on intact sandstone, single‐fractured sandstone, and double‐fractured sandstone using high‐precision hydro‐mechanics‐coupled triaxial experimental equipment to study the permeability evolution of fractured sandstone. The experimental schemes of the permeability tests are as follows: (a) under increasing confining pressure; (b) under increasing liquid pressure; (c) under cyclic loading and unloading deviatoric stress; and (d) under increasing confining pressure and deviatoric stress synchronously. Results show that liquid flow on fractured sandstone can be regarded as laminar flow with low velocity. The permeability and stress sensitivity levels of the fractured sandstone are higher than those of the intact sandstone. The permeability decreases in a negative exponential manner when the confining pressure increases but increases in a positively exponential manner when the liquid pressure increases. The increase in the deviatoric stress decreases the permeability, whereas unloading increases the permeability. The entire evolution of permeability is irreversibly reduced. As the confining pressure and deviatoric stress increase synchronously, the permeability decreases, and the decrease rate tends to be stable. These results can provide an important basis for prediction of the permeability evolution of fractured sandstone and for efficient oil and gas exploitation.

中文翻译：

---

复杂应力路径下裂隙砂岩渗透率的试验研究

石油和天然气是岩石孔隙和裂缝中的主要存储资源。在复杂的应力环境下​​，储集岩裂缝的渗透性演化直接影响着油气的流动，这在油气勘探开发中具有重要意义。使用高精度水力耦合三轴实验设备对完整砂岩，单裂隙砂岩和双裂隙砂岩进行了复杂应力路径下单个样品的渗透率测试，以研究裂隙砂岩的渗透率演化。渗透性试验的实验方案如下：（a）在增加围压下；（b）在增加的液体压力下；（c）承受周期性的装卸偏应力；（d）同步增加围压和偏应力。结果表明，裂隙砂岩上的液体流动可以看作是低速的层流。裂隙砂岩的渗透率和应力敏感性水平高于完整砂岩的渗透率和应力敏感性水平。当限制压力增加时，渗透率以负指数方式降低，而当液体压力增加时，渗透率以正指数方式提高。偏应力的增加会降低渗透率，而卸载会增加渗透率。渗透率的整个演变不可逆地降低。随着围压和偏应力的同步增加，渗透率降低，降低率趋于稳定。