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介绍了天然气水合物的勘查识别方法和浅表层天然气水合物的一些基本特征.水体回声系统观测到的水体火焰是海底甲烷气体喷溢的标志.在旁扫声呐图像上,海底甲烷气体喷溢位置表现为近似圆形的亮点异常,在海底剖面系统上表现为凸起地形,这些陆坡上的凸起一般几百米宽,几十米高.所有重力采样站位都是围绕这些海底气体喷溢位置布设的.岩心样品揭示,柱状样品大都含气.含气层段的沉积物分切面表现为特有的脱气构造.在两个重力取样站位采获天然气水合物样品.水合物呈薄层状与沉积物互层,薄层的厚度从几毫米到3cm不等,出现水合物的层段,肉眼可见的水合物约占柱样体积的5%～30%不等.在出现水合物的层段,仔细观察可以发现,在没有水合物的区域,微小的水合物颗粒存在于沉积颗粒之间.重力取样管中含有的气体并不完全是重力取样管上升过程中水合物发生分解形成的.在水合物的稳定域内,当气体含量不足时,地层中的气体仍可能以游离态的形式存在.一些特殊构造如泥火山、泥底劈等成为海底浅表层天然气水合物形成的中心.地层中的气体在沿这些特殊构造向上迁移的过程中部分气体在合适的温度压力条件下,在地层裂隙和孔隙度较大的地层中,和孔隙水结合形成天然气水合物.在这些构造以外的区域,由于沉积地层中的气体含量有限,其中的气体仍可能以游离气的形式存在,而不是以水合物的形式存在.
This paper introduces the methods of gas hydrate exploration and identification and some basic characteristics of superficial gas hydrate.The water flame observed by the water body echo system is a sign of methane gas spillover on the seafloor.In the submarine sonar image, The anomalous bright anomalies that appear as a nearly circular shape appear as convex terrain on the subsea system, and the bumps on these slopes are generally several hundred meters wide and tens of meters high.All gravity sampling stations are surrounded by these subsea gas spillages The core sample revealed that most of the columnar samples were gas-bearing.The sedimentary sections of the gas-bearing intervals were characterized by unique degassing structures.Gas hydrate samples were taken at two gravity sampling stations.The hydrates were thin The shape and interbedded sediments, the thickness of the thin layer ranging from a few millimeters to 3cm, hydrate layer occurs, the visible hydrate of about 5% to 30% of the column-like volume in the presence of hydrate A careful observation shows that in the areas without hydrates, fine hydrate particles are present between the deposited particles.The gas contained in the gravity sampling tube is not exactly the same as the hydrate In gas hydrate stable zone, when the gas content is not enough, the gas in the formation may still exist in free form.Some special structures such as mud volcanoes, mud bottom cleavage become the center of the formation of shallow surface gas hydrate During the upward migration of these gases along these special structures, some of the gases combine with the pore water to form gas hydrates in stratigraphic fissures and relatively large porosity formations under appropriate temperature and pressure conditions. Due to the limited gas content in sedimentary formations, the gas may still exist in the form of free gas rather than in the form of hydrates.