南海内潮影响下的水下溢油数值模拟研究

A significant factor in underwater oil spill simulation is the background hydrodynamic field, which can be obtained from a three-dimensional ocean model. It has been reported that the transport and fate of oil spilled underwater can be remarkably influenced by both the seawater stratification and vertical currents in the ocean. In the South China Sea (SCS), the existing oil/gas exploitation activities conducted by our country are mainly concentrated in the north part, where strong internal tides exist. Thus in this area, the potential influence of the strong internal tides on the underwater oil transport and fate cannot be overlooked. In this project, comprehensively utilizing the multi-source ocean observation data (including the satellite altimetry data and mooring array data) and available drilling information obtained from the offshore oil platforms in the northern SCS, the underwater oil spill process will be simulated by a numerical model, with two kinds of background hydrodynamic fields (containing or excluding internal tidal movements), which are derived from the simulation result of internal tides of multiple constituents via an isopycnic-coordinate internal tidal model with the adjoint assimilation method embedded and with the SCS circulation model data as its background. Based on a series of underwater oil spill numerical experiments, the main objectives of this project are, from the view point of ocean dynamics, to investigate the response of the underwater oil transport and fate to the seawater stratification and internal tides, and to reveal the role of internal tides in the prediction of underwater oil spill in the SCS. This project will contribute to the understanding of behavioral process of underwater oil spill, and then help to improve the ability of oil spill monitoring and early warning and risk prevention as well as the ability of emergency response after oil spill in the SCS, which will contribute an important guarantee to the safety in offshore oil/gas exploitation and production in the SCS.

水动力背景场是水下溢油数值模拟的关键要素。已有研究表明，海水密度层化和垂向海流均对水下溢油的输运和归宿有显著影响。目前我国在南海的油气开发活动主要集中在北部，该海域是一个典型的强内潮分布区，其强内潮的存在对水下溢油输运和归宿的潜在影响不可忽视。本项目拟以南海环流模式数据为大背景，综合利用南海北部多源观测资料（高度计资料和潜标观测资料）和现有的海洋石油平台钻井参数，利用一个等密度坐标内潮伴随同化数值模型，通过多分潮内潮数值模拟，为水下溢油模型构造有/无内潮运动的两种水动力背景场，进而通过水下溢油数值实验，阐明海水密度层化和内潮的存在影响水下溢油输运和归宿的方式和内在机理，揭示南海内潮在水下溢油预测中的重要作用。本研究有助于加深对水下溢油行为过程的认识，进而有利于提高南海溢油监测预警和风险防范能力以及溢油事故发生后的应急处置能力，为该海域海上油气田的安全生产提供重要保障。

南海北部拥有活跃的油气开发活动，其复杂的气象和水文环境，使得该海域的水下溢油事故难以处置，因此开展南海的水下溢油数值模拟研究，对加强该海域的溢油监测预警和风险防范能力以及溢油应急处置能力具有重要意义。本项目充分考虑了南海水动力环境的复杂性，利用数值模式深入开展了水下溢油行为和归宿研究。首先，对现有的水下溢油模型进一步完善，增加了海浪作用模块和泥沙作用模块，使模型能够支持海洋溢油的三维全过程模拟，并探讨了背景海流误差对海洋溢油模拟结果的影响；其次，提出了一个将油粒子分布转化为溢油浓度分布的有效方法，使模型结构更加合理，并揭示了在南海发生深海溢油事故时，在溢油点实施消油剂喷洒能够显著改变溢油的水下行为和分布；最后，在上述工作基础上，探讨了在南海实施溢油动力溯源的有效性，并针对水下的溢油源提出了三维动力溯源的实施方案，该成果能够为该海域海上无主油的判责提供重要的技术支持和方法储备。