用边界元数值模拟验证Hudson裂缝介质理论

裂缝介质各向异性的研究对于油气勘探与开发及地下工程建设均有重要意义。边界元法具有输入数据少、精度高等优点。本文依据Hudson裂缝介质模型,建立了纵波在裂缝介质中传播的边界元法数值模型,模拟了裂缝密度、裂缝纵横比以及裂缝填充物对纵波的传播速度和衰减因子的影响,探讨了波长与裂缝特征尺度的关系。结果显示,边界元法可以很好地模拟含裂缝非均匀介质中波的传播问题。波长和裂缝特征尺度的比值是等效介质理论能否成立的一个重要因素,裂缝饱和水后各向异性程度下降,裂缝密度对纵波传播速度及衰减因子有一定的影响。在地震长波长情况下,相同特征尺度的圆形干裂纹比薄的干裂纹对弹性波衰减更有效。

Using boundary-element numeric simulation to prove Hudson fractural medium theory

Studying anisotropy of fractural medium has important meaning for oil/gas exploration and development as well as underground engineering construction. The boundary element method is characterized by fewer input data and high precision. Based on Hudson fractural medium model, the paper creates numeric model of boundary element method that the P-wave propagates in fractural medium, simulates the influence of fractural density, aspect and infill on propagation velocity and attenuation factor,and probes the relationship between the wavelength and characteristic fractural scale. The results showed the boundary-element method can better simulate the issue of wave propagating in heterogeneous fracture-bearing medium. The wavelength-to-characteristic fractural scale ratio is an important factor whether the equivalent medium theory is correct or not, the anisotropic degree decreased when the fracture is water saturated, the fractural density has certain influence on P-wave propagation velocity and attenuation factor. Under the circumstance of seismic long wavelength, the circular dry fracture is more effective in attenuation of elastic wave than thin dry fracture when the characteristic scale is same.