基于模型正演的天然气水合物定量描述

Quantitative characterization of gas hydrate based on forward modeling

天然气水合物地震识别技术已从定性预测、半定量预测发展到定量描述,而在没有实测钻井资料的区域,如何开展天然气水合物量化描述是地震识别天然气水合物的难点。基于模型正演的天然气水合物量化描述技术提供了解决之道。文中以中国南海海域实际地震资料为例,利用地震多属性圈定天然气水合物发育区;再结合大洋钻探(ODP)数据不断调整沉积层速度和密度组合关系,建立与地震波组响应特征高相似度的水合物矿体正演模型;最后依据天然气水合物饱和度矿体与纵波阻抗关系量板,利用叠前弹性反演完成天然气水合物矿体空间分布及物性参数预测,为天然气水合物储量估算提供了基础。

Gas hydrate may be characterized qualitatively,semi-quantitatively,and even quantitatively using seismic data;but how to realize quantitative prediction in an undrilled prospect is a hard nut to crack.Forward modeling is a solution to this problem.Our case study focuses on a prospect in the South China Sea.The area with plausible gas hydrate is sited using several seismic attributes.The velocity and density of the sedimentary layer,after calibration using ocean drilling program(ODP)data,are then used for forward modeling to generate synthetic seismogram highly correlated with observed seismic data.After pre-stack elastic inversion,we predict hydrate distribution and its petrophysical properties in terms of the relation between hydrate saturation and Pimpedance.Our work provides information for the estimation of gas hydrate reserves.