The internal solitary waves (ISWs) with characteristic of large amplitude induce strong vertical mixing, vertical shear of horizontal speed and make notable impacts on the safety of the ocean engineering. In this study, data from three sets of submerged standard observations conducted in the land slope region west of Dongsha Island in the northern South China Sea (SCS) during 2021 were utilized to analyze the distribution characteristics of tidal and internal solitary waves in the oil and gas exploration area. The internal tides show surface-bottom intensified baroclinic mode-1 structure, and the major axis of tidal ellipse of O1 tidal constituent is larger than that of K1. During the whole observation period, there are four internal solitary waves (ISWs) clusters passed by the Liuhua oilfield area in total, and the appearance time lags 3∼4 days behind the astronomical spring tide of Luzon Strait. There are a total of 88 ISWs recorded at mooring of LH2, including 31 solitons and 57 ISW packets, and the averaged amplitude is 31 m. The daily appearance time for the ISWs concentrates between 4∼6 am, 11 am-1 pm and 6∼8 pm, and more than 45%of solitons appears between 4∼6 am. The results can provide a reference and technical support for the design and construction in SCS.
The South China Sea, colloquially known as the ‘second Persian Gulf,’ represents Chinese largest offshore oil and gas reserve. Numerous oil fields within the northern section of the South China Sea have been subject to extensive exploration and development. The oilfields coincide with the primary propagation axis of internal solitary waves in the northern region of the South China Sea. The immense energy conveyed by the internal solitary wave-induced potent currents can rapidly lead to the displacement of oil platforms. Additionally, the complexity of marine environmental fields, modulated by multi-scale background processes and influenced by internal solitary waves, escalates the risks associated with offshore construction operations.
