Numerical Simulation And Consequences Study Of Gas Pipeline Leakage In Shallow Sea

With the depletion of oil and gas resources on land,people have gradually turned their attention to the ocean.Compared with land pipelines,the environment of submarine pipelines is more complicated,the operational risk is greater,and the consequences of failure are more serious.In the event of an oil and gas leak in a submarine pipeline,it will cause huge economic losses and serious environmental pollution,and even cause adverse social impacts.For submarine gas pipeline leaks,natural gas leaks out in the water as a bubble plume jet until it overflows the surface.When natural gas moves to the surface of the water and spreads on the surface of the water,accidents such as burning and explosion may occur,posing certain environmental risks.In order to study the mechanism of leakage and diffusion of natural gas in seawater,the motion law of bubble plume jet is analyzed firstly,and the initial velocity formula of gas leakage in water body is derived.The biggest difference compared to land pipeline leakage is the change in external pressure.The motion interface tracking method was studied and summarized.By contrast,the VOF method was selected as the simulation method.Geometric model modeling and meshing were performed using ICEM CFD software,and the shallow sea gas pipeline leakage model was established using Fluent.The simulation results show the movement law of natural gas in seawater when the submarine gas pipeline leaks.Then choose the leakage diameter,water flow speed,pipeline pressure,water depth as the influencing factors to simulate.Through orthogonal test analysis,it is found that when the time to the surface is used as the test index,the primary and secondary relationships between the factors:water depth>leakage diameter>pipeline pressure>water flow velocity,water depth is an important factor,and the rest are secondary factors.When the size of the spilled area moving to the surface of the water is used as a test index,the primary and secondary relationships between the factors:water flow velocity>water depth>leakage diameter>pipeline pressure,all of them are significant influencing factor at this time.The situation in which the natural gas reaches the sea surface and diffuses in the atmosphere is analyzed.And the possible consequences of the accident were studied.When natural gas forms a flammable gas cloud and encounters a fire source,it may cause a deflagration phenomenon.When it forms a fire,the form of the fire has a fire similar to a pool fire,a jet fire,a fireball,a flash fire,and the like.The damage criteria for combustion and explosion are given.The phenomenon of gas diffusion and explosion in the atmosphere was simulated using Fluent software.The law of natural gas diffusion in the sea surface was analyzed.Natural gas first diffuses downwards and horizontally.Then,due to the influence of wind,the movement of the gas in the vertical direction is suppressed,and the main body of the gas cloud begins to fall,gradually approaching the sea surface and spreading horizontally along the sea surface.Then,the effects of wind speed,natural gas overflow rate and overflow position on the diffusion of natural gas were simulated,and the dangerous concentration range of natural gas was found.The detonation phenomenon of natural gas flammable gas cloud was stimulated.The flammable gas cloud encounters a small overpressure value of the fire source,It does not cause harm to people and equipment.The main hazards are from high temperatures and heat radiation.The paper completely considers the movement diffusion process of gas pipeline leakage in shallow sea areas.When an accident occurs,it provides a theoretical basis for relevant departments to formulate corresponding emergency and maintenance repair measures to minimize accident damage and economic losses.