Abstract:
There are several pipelines which are lying underwater for transportation of gases and other
hydrocarbons. These pipelines may get damaged due to several accidents, that results in release
of gas which rises as a plume and affects free surface. Risk assessments for offshore installations
involve the modeling of the consequences of a range of accident scenarios. This may include the
release of hydrocarbon inventory from top sides process equipment, subsea pipelines or risers or
blowout events. Release from risers, subsea pipelines and subsea blowouts will result in
dispersion of the hydrocarbon as it rises to the sea surface. This report presents a review of
current status of the modeling of subsea gas releases and assesses the implication of using the
modeling within a risk assessment.
Type of modeling available for subsea gas dispersion ranges from simple empirical
approximation to integral or CFD computer programs. A survey of operators showed that it was
the former empirical approximations which tended to be used within risk assessment studies, due
to their ease of use for large number of cases, although CFD has been used in a research context.
In all cases, lack of full scale data meant that the models have not been validated for the high
release rates common for rupture of subsea pipelines.
Here we studied about release of LNG from pipe and variation of properties along the depth of
sea. Plume structure and time taken by plume to reach surface has been noticed. Effect of water
current on plume is also studied. When LNG is released in water, it suddenly vaporizes, which
results in increase of temperature but it gets decrease along the path and with the time. Effect of
gas concentration on marine animals is studied.
