南中国海神狐海域天然气水合物 地震识别及分布特征

南中国海北部陆坡神狐海域是天然气水合物发育的有利地区,钻井取芯表明此区域的天然气水合物以细颗粒状分布于水合物稳定带内.以三维地震数据为基础,讨论海洋天然气水合物调查的高分辨率地震成像关键技术,综合利用不同的地球物理方法(阻抗反演、属性聚类分析及神经网络方法等),以钻井结果为约束分析不同方法对天然气水合物识别的适用性,确定利用属性聚类方法来获得神狐海域天然气水合物与游离气的三维空间展布特征.将钻井取芯结果与地质条件相结合,综合多方面地球物理信息,分析产生这一分布特征的地质原因,指出断层与裂缝是南海北部陆坡神狐海域水合物、游离气的分布模式及天然气水合物形成的主要地质控制因素.

Seismic identification of gas hydrate and its distribution in Shenhu Area,South China Sea

Shenhu Area of Northern South China Sea has favorable conditions for the occurrence and formation of gas hydrate,which was discovered in drilling cores and disseminated evenly within the hydrate stable zone(HSZ). Based on 3-D seismic data of marine geophysical investigation of gas hydrate,a variety of methods on gas hydrate identification were introduced,including high-resolution seismic imaging,impedance inversion,seismic attribute cluster analysis and neural network analysis. The applicability of various techniques was discussed and comprehensive interpretation of the results indicates that seismic attribute cluster analysis is the optimal technique for gas hydrate identification,by which the 3-D distribution of free gas and gas hydrate is presented and is identical with the drilling cores. Integrating the drilling cores with geological conditions,various geophysical information was used to analyze the geological cause of formation and the distributing model of free gas and gas hydrate,from which it can be concluded that faults and fractures are the important if not dominant factor in the formation and distribution of gas hydrate in Shenhu Area.