冷泉、羽状流与天然气水合物的联合探测分析

Joint detection and analysis of cold seepage,plume and gas hydrate

近年来我国在天然气水合物的勘探和开采上取得了重大标志性成果,与之相关的冷泉和羽状流的探测及数值模拟研究也取得了一定进展.基于前人对羽状流、冷泉和水合物在海底可视探测、声学探测、地震探测以及水合物实物取样方面所取得的研究成果,将海水中羽状流、海底冷泉与地层中的天然气水合物关联起来,定性的分析了冷泉、羽状流与水合物的内在联系.分析结果表明,冷泉、羽状流、水合物三者密切相关,海底羽状流通常发育于活动冷泉上覆水体中,羽状流是海底气体渗漏的直接表现形式,而冷泉区域下伏海底地层常富含天然气水合物;同时,水合物还可以与羽状流甲烷气泡共存于海水中,或是独立的水合物薄片,或是包裹在甲烷气泡外面;羽状流的气体来源可能是地层中水合物分解的甲烷气体以及未形成水合物的游离气.因此,冷泉羽状流对水合物勘探起到了很好的指示作用,在进行水合物识别勘探时,可以将海水中的气泡羽状流、海底冷泉与地层中的天然气水合物连接在一起,探讨羽状流与水合物赋存特征的地质与地球物理对应关系,寻找识别水合物的地球物理特征标志,从而形成一套自上而下的识别天然气水合物的立体体系.

In recent years,China has made significant and landmark achievements in the exploration and exploitation of gas hydrate,and some progress has also been made in the exploration and numerical simulation of cold seepage and plume.Based on the previous research results on visible detection,acoustic detection,seismic detection of plumes,cold seepages and hydrates as well as the physical sampling results of hydrates,the plume in seawater and cold seepage in the seafloor are associated with gas hydrate in formation,and the internal relationship among cold seepages,plumes and hydrates is analyzed qualitatively.The results show that cold seepages,plumes and hydrates are closely related.Submarine plume are usually found in the overlying water of active cold seepage,and the plume is a direct manifestation of submarine gas leakage,while gas hydrates are often rich in the underlying submarine strata in cold seepage areas.At the same time,hydrates can also coexist in seawater with methane bubbles of plumes,either as separate hydrate flakes,or as gas hydrate-coated methane bubbles.The gas source of the plume may be methane decomposed by hydrates in the formation and free gas without forming hydrates.Therefore,the cold seepage plume plays a very good indicator role in hydrate exploration.In hydrate identification exploration,we can link the bubble plume in sea water,submarine cold seepage and gas hydrate in the formation together,discuss the geological and geophysical corresponding relationship between plume and the occurrence characteristics of hydrates,and find the geophysical characteristic marks to identify hydrate,thus a top-down threedimensional system is formed to identify gas hydrate.