Research On Oil Leakage Law Of Submarine Pipeline Based On CFD

Oil leakage is a serious problem,once it happens,it will cause great threat and damage to the natural ecosystem and Marine environment.In order to better support the risk assessment and pollution control of the oil leakage in the Arabian Sea off the southeast coast of the Republic of Yemen,a two-dimensional transient numerical model of the local oil pipeline in the Arabian Sea off the southeast coast of the Republic of Yemen is established,and the oil leakage in the seabed is divided into two cases: exposed oil pipeline leakage and buried oil pipeline leakage.The effects of sea water velocity,leakage velocity,leakage Angle,buried depth of submarine oil pipeline,porosity of sea mud and crude oil density on the oil leakage diffusion characteristics and migration law in sea mud and water were studied.The relationship between lateral diffusion velocity of oil leakage in seawater and crude oil density in two cases is obtained.The research results can provide effective guidance and certain theoretical basis for the treatment of subsea oil pipeline leakage accidents.The results show that after oil leakage,a jet is formed in the water,and the time of oil diffusion to the sea surface increases with the increase of sea velocity.When the sea velocity increases from 0.1 m/s to 0.5 m/s,the time of oil diffusion to the sea surface increases from 14 s to 34 s.When the leakage diameter of the submarine oil pipeline increases from 30 mm to 70 mm,the time of oil diffusion to the sea surface is shortened from 19 s to 12 s.It decreases with the increase of leakage velocity.When the leakage velocity increases from 2 m/s to 8 m/s,the time of oil diffusion to the sea surface is shortened from 23 s to 9 s.When the leakage port direction is downstream of the top of the pipeline,the horizontal and vertical diffusion distances of crude oil leakage first increase and then decrease with the increase of the Angle between the direction and vertical direction of the leakage port of the submarine oil pipeline.The time for oil spill diffusion to reach the sea surface decreases first and then increases.When the Angle between the direction and vertical direction of the leakage port of the submarine oil pipeline is 60°,the crude oil can spread to the sea surface faster.When the direction of the leakage port is upstream of the top of the pipeline,with the increase of the Angle of the leakage port,the time of oil diffusion to the sea surface increases.When the Angle between the leakage port and the vertical direction of the submarine pipeline is 30°,the leaked crude oil moves almost vertically upward and can spread to the surface of the sea in a relatively short time.The leakage and diffusion characteristics of submarine buried pipeline are studied.The results show that the leakage oil products have a circular diffusion form in the sea mud.The flow velocity of sea water mainly affects the diffusion characteristics of oil products in the water body,but has little effect on the diffusion law of oil products in the sea mud area.When the leakage velocity increases from 2 m/s to 8 m/s,the diffusion time of the leaked oil product to the mud-seawater interface decreases from 10 s to 5 s.The width of the mud-seawater interface covered by oil products is about 3～5 m,and widened with the increase of the buried depth of the submarine oil pipeline and the extension of the leakage time.The time for the leaked oil products to reach the sea surface increases with the increase of the buried depth of the submarine oil pipeline.When the buried depth of the submarine oil pipeline increases from0.5 m to 1.5 m,The time for the oil to reach the surface increased from 20 s to 30 s.The permeability rate of the sea mud decreases with the increase of the sea mud porosity.The results show that considering the surrounding sea mud environment is helpful to determine the pollution range of oil leakage.The diffusion characteristics of different densities of crude oil after leakage in two cases are compared and analyzed.The results show that the smaller the density of oil,the greater the effect of sea buoyancy,and the greater the speed of horizontal diffusion along with sea water flow.Compared with the seabed exposed pipeline,buried pipeline leakage,oil diffusion rate is smaller.In addition,the relation between lateral diffusion velocity of oil leakage in seawater and crude oil density is obtained by further fitting,which can provide guidance for the formulation of offshore oil leakage emergency plan under different conditions.