Application of marine geophysical survey techniques to offshore geological survey before the drilling engineering

Pre-geological survey is essentially important to marine engineering constructing and determines the safety of the offshore operation. In this paper, the overall geological information for the aimed area should be obtained before the drilling platform was in position, so as to avoiding the existing geo-hazards while drilling. To address the problem, an integrated marine geological and geophysical survey was carried out by using echo sounding system, side-scan sonar system, sub-bottom profiling system and single channel and seismic streamer. The survey area was around a scheduled site in the South of China Sea, at which a certain survey well was designed in advance, and covering an area of about 1km(2). 24 geophysical survey lines were designed in this survey, including 21 main lines and 3 tie lines. After the data processing and analyzed, some potential geo-hazards, including a lot of sand waves, some patches and a paleo-river, were observed in the survey area. All of them might result in the inhomogeneous sinking of sediments and pose a serious threat to the coming offshore drilling, therefore, it should be paid more attentions on them.