南海东北部陆坡水合物钻探区BSR推导流体运移速率研究  

Research on fluid migration rates derived from BSR at the hydrate drilling area off the northeastern slope of the South China Sea

作　　者：王力峰[1] 陆敬安[1] 梁金强[1] 尚久靖[1] 王静丽[1] 

机构地区：[1]广州海洋地质调查局国土资源部海底矿产资源重点实验室,广东广州510075

出　　处：《地学前缘》2017年第4期78-88,共11页Earth Science Frontiers

基　　金：国土资源部国家专项(GZH201100303;GZH201100305);国家高技术研究发展计划"863"项目(2013AA092501);国家自然科学基金项目(91428205)

摘　　要：2013年广州海洋地质调查局在我国南海东北部陆坡海域实施天然气水合物钻探,获取了多种类型的高纯度水合物实物样品,进一步表明了南海存在丰富的天然气水合物资源前景。在此钻探之前,通过多年的地球物理、地球化学以及地质综合调查工作,积累了大量与天然气水合物赋存相关的各种地质数据。本文利用1D流体运移模型,结合热流站位的温压场数据以及多道地震数据所反映的BSR信息,计算了各个有效热流站位的流体运移速率,并结合钻探区的地质构造背景和钻探井位天然气水合物层位的分布情况,分析了流体运移速率分布特征,初步阐释了流体运移速率、构造背景以及与天然气水合物形成的相互关系。计算结果表明,钻探区流体运移速率数据分布区间为-25^+38cm/a,反映了钻探区构造背景相对复杂。流体运移速率分布具有规律性,主要受到断层和气烟囱的类别控制,可分为两大类。第一类为位于钻探区北部高地的继承性断层,断面直立陡倾并部分切穿海底,伴有大型气烟囱顶部或数量众多的侧翼小型活动正断层,为深部大规模流体运移提供了充足通道。受此类地质条件控制的流体运移速率表现为幅值波动较大,天然气水合物多发育在海底浅层,且呈现多层分布。第二类为位于钻探区西南部以及东部较大水深的滑动断层以及小型气烟囱,断层主体表现断层面清晰,断面较缓,刺穿尺度较短,气烟囱发育也比较晚,一定程度上限制了来自深部流体运移的规模。受此类地质条件控制的流体运移速率表现较为缓和,流体运移速率波动范围小,天然气水合物多发育在海底深层。In 2013,Guangzhou Marine Geological Survey conducted a drilling expedition on the continental margin along the northeastern slope of the South China Sea,successfully recovering core samples containing gas hydrate in various types,which further confirmed the existence of a huge resource prospects of gas hydrate in the South China Sea.Prior to the expedition and following several years of geophysical,geochemical and comprehensive geological investigations,we obtained reliable data which provide abundant evidence for the occurrence of gas hydrate around the drilling area.In this paper,by employing a simple 1Dvertical fluid flow model with the BSR interpretation of multichannel seismic data and heat flow measurements,we calculated fluid migration rates in valid heat flow sites,then analyzed the characteristics of rates distribution through a combination of knowledge of geological background and occurrence depth of gas hydrate-bearing layers,attentively delineating the relationship among fluid migration rates,tectonic background and gas hydrate occurrence in the drilling area.The initial results show that 1D vertical fluid rates are between-25and38cm/yr,indicating complex geological background in the drilling area.The distribution of fluid migration rates has two distinct patterns,apparently being controlled by the faults and diapirs in two particular categories.The first one is concentrated within the northern highland of the drilling area in relation to inherited steep faults,apart of which,in particular,often evolve upward to the seafloor.In addition,several domes of large diapirs develop underneath and a number of active mini faults grow in the flanks,providing feeding channels for fluid migration from deeper sediment.Thus,the rates of this category manifest a pattern of dramatic variations,and gas hydrates occur in shallow multi-layers of sediments.The second one is distributed in the southwestern and eastern lowland of the drilling area.Besides a few of small young diapirs developing underneath,some low-angle gl

关 键 词：南海东北部陆坡 天然气水合物 钻探 流体运移速率 似海底发射层 

分 类 号：P618.13[天文地球—矿床学]