含流体复杂孔隙介质地震波衰减与频散

Seismic wave velocity attenuation and dispersion in the patchy saturated medium with complex pores and cracks

含流体孔隙介质中地震波的速度频散和衰减在指导复杂储层含油气性识别领域具有重要意义.本文构建了包含微观挤喷流与介观层间流影响的跨尺度模型,并使用求解介质等效模量的方式得到了模型中地震波的频散速度与衰减因子,克服了前人在高频段计算结果出现异常值以及不同尺度衰减峰无法分离的缺陷.在该双尺度模型的基础上,本文又综合考虑宏观尺度Biot流,将三种地震波衰减理论耦合,建立了相对统一的三尺度地震波衰减岩石物理模型.在Biot理论框架下,分析了非均匀性流体、孔裂隙结构、微观挤喷流以及介观层间流对流体压力与弹性模量的影响,得到了该三尺度模型中地震波的波动方程,并求解得到了相应的地震波衰减与频散曲线,分析了不同介质参数对衰减与频散曲线的影响.我们推导了在该模型上覆均匀各向同性介质情况下,分界面处各类极性波的反射、透射系数特征方程,并得到了随频率以及入射角变化的反射、透射系数三维曲面.

The velocity dispersion and attenuation of seismic waves in fluid-saturated porous media are of great guiding significance in complex oil and gas reservoir identification. We construct a dual-scale model that includes the influence of microscopic squirt flow and mesoscopic interlaminar flow. And the dispersion velocity and attenuation factor of the model are obtained by calculating the effective moduli, which overcomes the defects of abnormal values at high frequency band and the inseparability of the attenuation peaks at different scales. On the basis of the dual-scale models, we establish a relatively unified three-scale seismic wave attenuation rock physics model by considering the macroscopic Biot flow and coupling the mechanisms of three different scale. Under the Biot theory, the effects of inhomogeneous fluid, pore and crack structure, microscale squirt flow and mesoscale interlaminar flow on fluid pressure and elastic modulus are analyzed, and the wave equation of seismic wave in the three-scale model is obtained. The wave equation is solved to obtain corresponding seismic wave attenuation and dispersion curves, and analyze the influence of different media parameters on the attenuation and dispersion curves. The equations of reflection and transmission coefficients are derived under the assumption that the overlying medium is homogeneous and isotropic. The three-dimensional surfaces indicating the variation of reflection and transmission coefficients with frequency and incident angle are obtained.