摘要
含流体孔隙介质分界面上的反射和透射系数对储层表征和流体识别至关重要.本文考虑含流体孔隙介质与弹性介质间分界面, 基于等效Biot理论描述孔隙介质中介观流作用, 研究了分界面上反射系数频变机理.将势能波函数表示的位移和应力代入到分界面处连续性边界条件, 推导了纵波从孔隙介质入射和弹性固体入射两种情况下反射系数计算公式.通过对典型地质模型的正演计算, 得出了反射系数振幅随入射角和频率的变化规律, 揭示了介观流的影响机理.结果表明, 介观流引起地震频带内快纵波的速度频散和衰减, 并导致10 Hz到1 kHz频带间的反射系数频散.相比波从弹性固体入射时结果, 波从孔隙介质入射时的反射频散特征更为显著, 并受非均匀角的影响.在低频时, 反射系数与经典Zoeppritz方程计算结果一致, 而高频时, 介观流作用消失, 反射系数与无介观流时计算结果一致.分析这些特征对利用多尺度反射地震数据进行精细储层预测和流体识别具有重要意义.
Reflection and transmission coefficients at the interface of porous media are crucial for reservoir characterization and fluid identification. This work considers the interface between the porous medium and an elastic solid and investigates the frequency-dependent reflection coefficients, based on the effective Biot theory to account for the mesoscopic flow in porous media. By substituting the displacements and stresses, expressed in terms of the potential wave function, into the boundary conditions at the interface, we derive the reflection coefficients for two different cases, namely, P1-wave incident from the porous medium and P-wave incident from the elastic solid. Numerical computation on a typical geological model gives the variation in magnitude of the reflection coefficients as a function of incidence angle and frequency, which reveals the influence of mesoscopic flow. The results indicate that the mesoscopic flow induces the velocity dispersion and attenuation of the fast P1 wave over the seismic frequency band, and consequently results into the dispersion of reflection coefficients between 10 Hz and 1 kHz. Compared with the results when the wave is incident from the elastic solid, the dispersion effect is more significant when the wave is incident from the porous medium, which is also affected by the inhomogeneity angle. At the low frequencies, the reflection coefficients are consistent with those of the classical Zoeppritz equation, whereas at high frequencies, they overlap with the results when the mesoscopic flow is absent. Those analyses can be of great significance for reservoir prediction and fluid identification using the multi-scale reflection seismic data.
作者
严家轩
王恩江
熊方菲
YAN JiaXuan;WANG EnJiang;XIONG FangFei(Key Lab of Submarine Geosciences and Prospecting Techniques,MOE,College of Marine Geosciences,Ocean University of China,Qingdao 266100,China;Frontiers Science Center for Deep Ocean Multispheres and Earth System,Qingdao 266100,China)
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2024年第11期4289-4308,共20页
Chinese Journal of Geophysics
基金
国家自然科学基金(42174148,41804095)资助。
关键词
频变反射系数
介观流
频散与衰减
等效Biot理论
边界条件
Frequency-dependent reflection coefficient
Mesoscopic flow
Dispersion and attenuation
Effective Biot theory
Boundary conditions
