New Type Energy||Renewable Energy

In 1934, Hammerschmidt showed that the formation of gas  hydrates  was responsible for blocking pipelines. Considering the significant economic risks in the gas and oil industry, much of research has been conducted by the petroleum industry in order to inhibit this phenomenon.

In fact,  hydrate  propagation tends to gradually form a plug that separates the pipe into two pressure sections: a high pressure section between the well and the plug and a second section at low pressure between the plug and the recovery division. In the upstream section, a pipe blast can occur due to the pressure rise. The plug can also behave as a projectile that destroys the pipe when the pressure difference between the upstream and downstream sections increases. Both events can imperil personnel safety and damage production equipment. Preventing  hydrate  agglomeration in pipelines is a real challenge, since it happens in hostile environments, such as the Arctic where very low temperatures are encountered, and in subsea pipelines where pressure can reach high levels.
Four main processes were investigated in order to combat  hydrate  plugs and ensure regular flow: chemical, hydraulic, thermal and mechanical processes. The chemical method, which can be used either to prevent or to remove plugs, consists in injecting additives in the pipe that act differently on  hydrate  agglomeration according to whether the inhibitors are thermodynamic, kinetic or dispersant. The thermodynamic inhibitors, generally methanol or glycols, aqueous electrolyte solutions, are injected in order to shift the equilibrium temperature, thus enabling gas  hydrate  crystallization. This method is efficient but limited by the large quantity of additives implemented (60 wt%), which is, moreover, difficult to recover from water, and by the corrosive properties of salts (electrolytes). A new generation of additives has been developed: dispersants such as QAB (quaternary ammonium bromide) that prevent  hydrate  agglomeration; kinetic inhibitors, generally polymers, that slow down  hydrate  crystal growth so much that it cannot disturb oil transport. Only small amounts of dispersant and kinetic inhibitors are required to prevent pipeline plugging, making them economically attractive.
The hydraulic removal method is based on the dissociation of the  hydrate  plug by depressurization. This method seems promising, given the porous structure of the gas pipeline plugs. However, it is not suitable for liquid hydrocarbons, since depressurization induces its vaporization.
The thermal method consists in delivering locally a heat flow towards the plug through the pipe wall in order to raise the system temperature above the  hydrate  formation point. This method is possible for external pipelines but unsuitable for subsea equipment.
Finally, a mechanical method, such as pipeline pigging, can be used to prevent  hydrate  plugs. Pipeline pigs are inserted into the pipe and travel throughout the pipeline, driven by product flow. These projectiles then remove the obstacles or deposits they encounter.
Despite all these methods, pipeline blockage by gas  hydrates  remains a concern in the oil and gas industry, and ongoing research is being conducted in this field. In particular, transmission lines are increasingly being placed in deepwater pipelines. The selection of an optimal method involves taking into account the type of products (gas, liquid hydrocarbon or crude oil) transported and the type of pipeline (external, subsea) used. Sometimes, several processes can be combined to destroy plugs more efficiently, for instance, chemical inhibitors can be used in conjunction with a mechanical removal method.