海底输气管道泄漏天然气扩散风险研究

Research into the risk of natural gas spread from submarine natural gas pipeline leakage

针对海底输气管道在服役过程中发生泄漏引发天然气扩散问题,采用计算流体动力学CFD方法,建立海底输气管道泄漏天然气扩散后果预测与评估模型。围绕泄漏天然气在海水中以及从海面溢出后在大气中扩散两种场景,预测天然气在海水中的运移轨迹,评估天然气上浮时间、溢出位置和溢出区域大小等关键风险参数。预测天然气从海面溢出后在大气中的扩散过程,评估天然气在海面形成的危险区域范围,并考虑海面天然气爆燃场景,评估爆燃超压、火灾高温和热辐射等伤害参数的变化规律。研究表明:天然气水下扩散能够引起海面表层海水密度降低,在海面形成的涌流效应,可能对海面浮式结构物的稳定性产生影响;天然气海面扩散风险主要为可燃气云被引燃之后可能发生爆燃事故;CFD模型能够实现对海底输气管道泄漏天然气扩散风险的有效预测和评估,可为海底输气管道泄漏风险管理与应急决策提供参考。

In terms of the risk from submarine natural gas pipeline leakage,a computational fluid dynamics(CFD)model is developed to predict and assess the consequence of natural gas escape. In the present study,both of the scenarios that natural gas escapes into sea water and above the sea surface are included. The escape trajectory of natural gas in seawater is predicted,and the critical risk parameters like rise time,spill position and spill region etc. are assessed using the developed CFD model. Based on the assessment results of natural gas movement in seawater,the transport process and corresponding danger areas of natural gas above the sea surface are also determined. In addition,considering the likelihood of ignition,the deflagration scenario of natural gas above sea surface is simulated and analyzed in the present study for assessing the overpressure,high temperature and heat radiation,etc. The study results indicate that natural gas escape in seawater could lead the density of surface water to decrease,and form a 'boiled' zone or fountain,which would have an effect on the stability of floating structures on sea surface. A deflagration accident may occur when the natural gas above sea surface is ignited by a ship or platform. The CFD model developed in this paper could be employed to predict and assess the risk of natural gas from submarine pipeline leakage effectively,and provide an educational reference for risk management and emergency decision-making for submarine natural gas pipeline leakage.