Perm Scientists Find a Way to Prevent Hydrogen Sulfide Pipeline Blockages

During the extraction and transportation of natural gas, hydrates form inside pipelines. These are solid crystalline compounds that resemble ice. They accumulate on pipe walls and can block the pipeline. As a result, production stops and companies suffer losses worth billions.

Scientists from Perm Polytechnic have found a solution. They experimentally studied hydrate behavior in the presence of hydrogen sulfide for the first time in Russia and developed a mathematical model that predicts hydrate formation with more than 99.5% accuracy. The technology will help prevent accidents and reduce the use of costly chemical reagents used to combat hydrates. It will also enable safer development of “sour gas” fields in the Arctic and on offshore shelves, the university’s press service told IT Russia.

“Sour” Gas

Up to 40% of Russia’s explored natural gas reserves are classified as difficult to extract and contain aggressive impurities, including hydrogen sulfide. This component makes gas “sour” and changes the conditions under which hydrates form. Its molecules easily integrate into the forming crystals, meaning blockages can appear even where they normally would not occur.

The problem is especially acute in the Arctic. At low temperatures the risk of hydrate formation is highest, while many new deposits also contain hydrogen sulfide. Because of hydrate plugs, wells can remain idle for up to 18 hours a month, leading to significant losses.

Experimental data on hydrate behavior in the presence of hydrogen sulfide are scarce worldwide because the gas is toxic and highly corrosive. Research requires specialized equipment. Scientists at Perm Polytechnic built a sealed laboratory system with a high-pressure reactor and a temperature control system that allows them to work safely with hydrogen sulfide. For the first time in Russia, researchers can now study hydrate behavior in a “sour” environment in detail.

Not Afraid of Hydrogen Sulfide

For comparison, standard calculation methods used for conventional gas can produce deviations of up to 7–8% when hydrogen sulfide is present. As a result, engineers may fail to detect the risk of hydrate formation or may overcompensate and increase spending on prevention. The new model allows safe operating regimes for sour gases to be calculated with high precision.

Special substances known as inhibitors prevent hydrates from forming. They slow crystal growth and stop crystals from sticking together to form large plugs. However, their effectiveness decreases in the presence of hydrogen sulfide. Earlier, another group of Perm Polytechnic scientists developed new inhibitors based on polyquaterniums that remain effective even in hydrogen sulfide environments. The new mathematical model will allow engineers in the field to select safe operating regimes in advance.