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由于裂缝及所含流体的综合作用,含裂缝介质不仅具有速度各向异性,还具有显著的衰减各向异性。衰减各向异性分析可应用于裂缝产状、裂缝密度和尺度等的估计,为储层识别提供重要信息。本文从理论上推导了ATI介质(对称轴沿任意方向的横向各向同性介质)中P波衰减各向异性关系,并据此改进了ATI介质中P波衰减各向异性的测量方法,避免了现有的基于泰勒展开改进的谱比法在应用于宽方位或全方位数据时误差较大的问题,同时基于P波衰减各向异性分析可对裂缝倾角和方位角进行初步估计。结合P波衰减各向异性分析和S波速度各向异性分析,可实现小尺度裂缝的裂缝密度和裂缝尺度联合反演,相比于单独使用横波速度各向异性分析方法或单独使用P波衰减各向异性分析方法,其反演结果更准确、收敛性更好。本文将衰减各向异性分析应用于中国东部某油田的微地震数据,通过衰减倾向各向异性分析提取的裂缝倾角,与微地震监测结果相符。
Due to the combined action of fractures and fluids, the fractured media not only have velocity anisotropy, but also have significant decay anisotropy. Attenuation anisotropy analysis can be applied to the estimation of fracture occurrence, fracture density and scale, which provides important information for reservoir identification. In this paper, we theoretically deduce the anisotropy of P-wave attenuation in ATI media (transversely isotropic media with symmetric axis along any direction), and then improve the measurement method of P-wave attenuation anisotropy in ATI media to avoid The existing Taylor-based improved spectral ratio method is more error-prone when applied to wide-azimuth or omnidirectional data, and preliminary estimates of dip and azimuth of fractures can be made based on P-wave attenuation anisotropy analysis. Combined with P-wave attenuation anisotropy analysis and S-wave velocity anisotropy analysis, it is possible to realize the joint inversion of fracture density and fracture scale of small-scale fractures. Compared with the method of shear-wave velocity anisotropy alone or P-wave attenuation alone Anisotropy analysis method, the inversion results more accurate, better convergence. In this paper, the attenuation anisotropy analysis is applied to microseismic data in a field in eastern China. The fracture dip extracted by decay propensity anisotropy is consistent with the microseismic monitoring results.