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1 前言 在未勘探地区最主要的问题是确定是否有烃类的聚集发生过。由于烃类的形成期决定了资源量,因此第二个问题就是油气是否存在。海底地表地球化学是在未勘探地区所应用的方法之一。这项技术是建立在这样的假设基础上,即地下的烃通过相对局部的断层或通过在区域性地震资料上未分辨的断裂逸散到海底,在海底沉积物中形成烃类指纹。尽管此项技术在许多地区已经证明是成功的,但迄今为止,地表地球化学应用于挪威大陆架的未勘探地区,其成功率却有限。烃逸散常与到达海底的作为逸散通道的断层有关(如墨西哥湾),但在北海大多数主断层被厚的未发生断裂作用的白垩纪和第三纪沉积物覆盖,那里逸散是沿着小断裂的通道进行的(图1)。
1 Introduction The most important issue in unexplored areas is to determine if any hydrocarbon accumulation has occurred. As the formation of hydrocarbons determines the amount of resources, so the second question is whether oil and gas exist. Seabed surface geochemistry is one of the methods used in unexplored areas. This technique is based on the assumption that subterranean hydrocarbons escape to the sea floor through relatively localized faults or through undissolved fractures on regional seismic data, forming hydrocarbon fingerprints in sea floor sediments. Although this technique has proved successful in many areas, the success rate of surface geochemistry applied to the unexplored areas of the Norwegian continental shelf to date has been limited. Hydrocarbon fugitives are often associated with faults that reach the seafloor as escape channels (eg, the Gulf of Mexico), but most of the major faults in the North Sea are covered by thick, unbroken Cretaceous and Tertiary sediments that are Along the small fracture of the channel (Figure 1).