岩体裂隙渗透率应力敏感性分形研究

Fractal Study on Stress Sensitivity of Fracture Permeability

应力作用下裂隙性储层的渗流问题在油气勘探开发等工程领域有着重要的研究价值。在应用分形理论和流体力学的基础上,建立了考虑应力敏感性的裂隙渗透率预测模型。通过定义归一化渗透率研究有效应力作用下裂隙渗透率与岩体岩性的相关性。预测模型不使用任何经验常数,各参数都具有明确的物理意义。模型的预测结果与相关的试验数据的吻合程度高,验证了模型的有效性。理论分析结果表明,裂隙内流体的归一化渗透率随有效应力的增大呈现出显著降低的变化趋势,岩体的杨氏模量和泊松比越大,迂曲度分形维数越小,归一化渗透率越大。建立的预测模型可以有效描述应力作用下裂隙流体的渗流特征。

The seepage problem of fractured reservoirs under stress has important research value in engineering fields such as oil and gas exploration and development. Based on the application of fractal theory and fluid mechanics, a fracture permeability prediction model considering stress sensitivity was established. The correlation between fracture permeability and rock mass lithology under effective stress rock was studied by defining normalized permeability. The prediction model did not use any empirical constants, and each parameter had a clear physical meaning. The prediction results of the model were in good agreement with the related experimental data, which verified the effectiveness of the model. Theoretical analysis results showed that the normalized permeability of the fluid in the fracture decreased significantly with the increase of the effective stress. Rock mass with the larger Young’s modulus and Poisson’s ratio and the smaller fractal dimension of tortuosity will get a larger normalized permeability. The proposed model can effectively describe the seepage characteristics of fluid in fractures under stress.