Study On Combustible Gas Leakageage And Diffusion By CFD Simulation

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 context, this paper employs the CFD software– FLUENT to simulate and evaluate the combustible gas leakageage on offshore platforms of a gas field.Based on the preliminary investigation and analysis of the gas field and according to the facilities performance and the divided risk area of the platforms, the paper analyzes the probability distribution of various inherent faults of the equipments including the separator, washing tank, accelerant device, ball valve, butterfly valve, gate valve, needle valve and compressor, etc. and explores the characteristics of the inherent risks, including the leakageage, of the marine petroleum production equipments. On the basis of the data in the OREDA database, the number and size of the corresponding valve, flange, device attachment and pipeline of all the equipments in the center platform and wellhead platform are summed to estimate the leakageage frequency of various units of the platforms.It is shown from the calculated results that the contact tower and the testing separator of the center platform and wellhead 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.