中国油气勘探的一个新领域——深水牵引流沉积

A New Field of Petroleum Exploration in China:Deep-water Traction Current Deposits

深水牵引流沉积主要分为等深流沉积和内波内潮汐沉积两类。前者可形成巨大的堆积体——等深积岩丘,其规模可与海底扇相比拟。现代海洋大陆坡及陆隆地带等深积岩丘非常发育;古代地层记录中也有等深积岩丘,如已开采数十年的阿拉伯克拉通白垩系等深积岩丘油田。后者则不仅可形成分选极好的砂级沉积物,而且可形成规模巨大的“沉积物波”,并成群成带地出现。海洋中沉积物波的迁移可形成巨大的沉积体。在世界各大洋深盆海底,均有大范围分布的现代大型沉积物波。中国地层记录中的大型沉积物波,首先在塔里木盆地塔中地区中一上奥陶统中被识别出来,并有良好油气显示。认为中国的广大地区发育有多个时代的海相深水沉积,深水牵引流沉积储集层是中国21世纪油气勘探具巨大潜力和现实可行性的新领域。其油气勘探首选地区是塔里木盆地、扬子地台南缘和鄂尔多斯西缘。

Deep-water traction current deposits mainly include contour current deposits and internal-wave/internal-tide deposits.The former can form giant sedimentary bodies,the contourite drifts,which are comparable to large submarine fans in extent. Contourite drifts are well-developed along modern continental slopes and rises.The ancient contourite drifts in the strati- graphic record were reported in literatures,such as the Creta- ceous contourite drift on the continental margin of Arabian Cra- ton,a huge oil field that have been produced for several decades.The latter can not only form well-sorted sand-size deposits but also large-scale sediment waves occurred in groups.The sediment waves migrated in oceans can bring in a large-soale sedimentary body.There are large-scaled modern sediment waves wide-distributed on the deep-sea floors of the every ocean basin.A large-scaled sediment wave reservoir in stratigraphic record,which has good oil shows,was first rec- ognized in the Middle-Upper Ordovician strata in Tarim Basin. Deep-water marine deposits were well-developed in the vast areas of China in many geological times so that the reservoirs of deep-water traction current deposits should be a new greatly potential field for China's petroleum exploration in 21 century. The preferred regions should include Tarim Basin,south margin of Yangtze Platform and west margin of Ordos Basin.