非胶结含水合物沉积物修正等效介质速度模型及其地震波场特征研究

Modified effective medium modeling and seismic wave field in un-cemented marine sediments with hydrates

通过数值分析,发现对应于悬浮模式、颗粒接触模式的等效介质模型A,B预测的含水合物沉积物纵波速度、横波速度及泊松比存在物理认识上的缺陷,单独考虑水合物微观模式为悬浮模式或颗粒接触模式并不合理.认为非胶结水合物的微观模式与其饱和度存在关联,并运用拉格朗日插值方法建立了新的非胶结含水合物沉积物修正等效介质速度模型.该模型体现了水合物饱和度对于水合物微观模式的影响,数值分析结果表明新模型预测结果更合理.基于新模型对非胶结含水合物沉积物的地震波场进行了数值模拟,探讨了似海底反射及空白带的形成机理,对实际水合物地震勘探中发现的不同地震波场特征对应的水合物分布模式进行了解释.

Elastic-wave velocity estimation in marine sediments with hydrates is an important part of hydrate seismic survey method and engineering. Suspending model and grain contact model are two main hydrate microscopic patterns for the non-cemented sediments with hydrates. Through numerical analysis, we discovered the velocity of compression wave and transverse wave and the Poisson＇s ratio forecasted by suspending model and grain contact model have bugs in physical understanding. Considering the hydrate microscopic model as the suspending model or grain contact model singly is unreasonable. We point out that the hydrate microscopic model is related with the hydrate saturation and established a modified effective medium modeling of non-cemented sediments with hydrates using the Lagrange interpolation method. This model considers the effect of hydrate saturation on the hydrate microscopic model, and the numerical analysis indicated that the new model is more reasonable. We made numerical simulation of seismic wave field based on the modified effective medium model and studied the characteristics and mechanism of BSR and blanking zone, and then expounded some phenomena observed practically based on the possiblly existing models.