可燃气泄漏扩散的CFD研究

Study on combustible gas leakageage and diffusion by CFD simulation

海洋石油是具有高风险的行业,尤其是开采高压天然气的生产设施,现场有大量静密封点,极有可能发生可燃气泄漏。计算流体力学(CFD)方法可以实现分析、判断和预测可燃气泄漏后所影响到的扩散区域,在事故的预防、控制以及平台应急、逃生方面均具有重要的指导意义。本文在对某气田群进行前期调查和深入分析的基础上,根据平台上设备实际运行情况,选择具有代表性的泄漏点。运用计算流体力学模拟方法,合理搭建平台的物理模型,选择适宜的扩散方程和边界条件,对该海上平台可燃气泄漏进行了模拟计算。计算结果表明平台上接触塔和测试分离器的泄漏概率最大,建议重点加强对上述设备单元内的管线、阀门、法兰等日常维护、保养,从预防角度进行风险控制:中心平台上接触塔、生产分离器和天然气清管球发射器,井口平台上井口采气树、测试管汇和测试分离器运行压力较高,泄漏后扩散后影响的范围、潜在升级的后果比较严重,建议对上述重点设备开展基于风险分析的检测工作;甲板空间内设置的防火墙、中控等房间形成阻挡物,在一定程度上影响了甲板空间内的通风效果,当风向为阻挡物的上风向时,天然气泄漏后扩散影响范围较大,此时应对整个影响区域内的明火源进行严格控制。基于CFD计算结果,可以有效划分平台的危险区域和火灾区域,为应急程序的细化提供参考依据,为事故发生后的应急指挥、选择正确的逃生路线提供参考。

The marine petroleum exploitation is a high-risk industry,particularly at the high-pressure natural gas extraction section,where there are a great number of static sealing points,so combustible gas leakageage can very likely occur.Computational Fluid Dynamics（CFD） can accurately analyze,fix and predict the affected region of the combustible gas leakageage,which is instructive to accident prevention and control,platform emergency and evacuation mechanism,etc.In this paper,on the basis of prophase investigation and in-depth analysis, according to the actual operation status of equipment,the main leakageage points on the platform were selected.Using computational fluid dynamics simulation,building the reasonable physical model,selecting the appropriate diffusion equation and the boundary condition,CFD simulate of gas leakageage on the platforms was carried out.It is shown from the calculated results that the contact tower and the testing separator of the platform are most inclined to leakageage gas,so it is recommended to enhance the daily maintenance of the pipelines,valves and flanges in the above units to prevent and control accidents.The contact tower,production separator and gas pigging launcher of the center platform,gas well Christmas tree,testing manifold and testing separator of the wellhead platform have higher operation pressure with more serious consequences and larger range of influence after the leakageage and diffusion,so it is recommended to do inspection on the above key equipments based on risk analysis.The firewall,control room and other rooms will,to a certain extent,affect the ventilation in the deck space, and there will be a larger range of influence after the gas leakageage when the wind is on the windward side of the above barriers.At this point, it is recommended to strictly control the ignition sources over the whole region of influence.The danger zone and fire zone of the platforms can be effectively divided with the help of the calculated CFD results,which provide reference for the refinement of the emergency program,the post-accident emergency command and the selection of correct escape routes.