Understanding Corrosion in Water Pipelines: A Guide for Pipeline Designers


Acid Gas Injection

Last updated: April 24, 2018

What Does Acid Gas Injection Mean?

Acid gas injection refers to injecting or disposing of acid gas into a suitable underground zone similar to the ones used for water disposal during oil and gas drilling activities.

Acid gas is a classification of natural gas, which contains impurities in significantly large quantities to make the gas acidic. Acid gas contains large quantities of hydrogen sulfide (H2S) and carbon dioxide (CO2). This gas can damage pipelines via corrosion, which ultimately leads to leaks in the pipeline.


Corrosionpedia Explains Acid Gas Injection

Acid gas is sometimes thought to be same as sour gas; however this is incorrect because sour gas only consists of hydrogen sulfide and natural gas, whereas acid gas consists of both hydrogen sulfide and carbon dioxide in large quantities. Carbon dioxide is very acidic and provides the acidic nature to natural gas.

Acid gas is raw gas that must be treated before it is allowed to enter pipelines. Impurities such as hydrogen sulfide, carbon dioxide, debris and sand are removed through an amine gas treatment process. This is done in an amine regeneration column. Before injection, the acid gas is processed in this column where it is compressed to sufficient pressure and sulfur compounds and carbon dioxide compounds are removed. The acid gas is then injected into the ground or flared in the atmosphere. There are three steps associated with the acid gas injection process:

  1. Acid gas is compressed and sulfur compounds and carbon dioxide compounds are removed.
  2. The gas is transported through pipelines to a suitable place where it can be injected or flared.
  3. The gas is forced into an injection well.

Acid gas corrosion of low-alloy steel occurs mainly in the presence of a liquid aqueous phase. The corrosion manifests itself as general metal loss corrosion or pitting corrosion. When these occur, atomic hydrogen is generated. Because atomic hydrogen can penetrate steel, this can lead to hydrogen-induced cracking, blistering or sulfide stress cracking, resulting in sudden failure.


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