GEO-HAZARDS AND THEIR DISTRIBUTION IN THE MIDDLE AND SOUTH PARTS OF XIHU SAG, EAST CHINA SEA

The middle and south parts of the Xihu Sag are rich in petroleum resources in the East China Sea. The oil and gas fields of Pinghu and Chunxiao have already been in production for years. In the past decades, a large number of site investigations were conducted to ensure the safety of drilling platforms. However, there are still a few drilling platforms suffered from punch-through and uneven sinking, due to lack of regional understanding of the characteristics, distribution and mechanism of the geo-hazards in the region. After careful study of the past marine investigation data, this paper made a further analysis of geo-hazards and their distribution, including sand wave, seabed scour, pockmark, shallow gas, high pressure shallow gas, buried channel, buried slide and shallow micro fault. Although these geo-hazards are relatively stable currently, accidents will happen if they are trigged by other unforeseen factors. Based on the data from the past engineering geophysical survey in this area, this paper dealt with the types and distribution pattern of different geo-hazards in this area that would provide good reference for follow-up site investigations.