Distribution characteristics and genesis analysis of submarine shallow gas in Ningde coastal area, Fujian Province

In recent years, a series of coastal geohazard problems have been exposed during the development of the coastal area, among which the impact of submarine shallow gas is particularly serious, seriously destroying the structure stability of the submarine sediment layer as an important factor affecting the construction safety of offshore engineering. In order to ascertain the distribution characteristics and geneses of shallow gas in Ningde offshore, by means of single-channel seismic, shallow stratigraphic profile, side-scan sonar and other methods, a number of shallow gas hosted in form of layers and clusters was found in the depth of 20 m underground in the area. Based on the analysis of the distribution characteristics and seismic profiles of shallow gas in this area, in comparison with previous genesis analyses of shallow gas in neighboring areas and in combination with the geological evolution and sedimentary history of Ningde sea, we basically determined that the shallow gas in Ningde sea were derived from biogenic origin, and discussed the harm of shallow gas to offshore engineering construction and its preventive measures.