Microorganisms in the oil and gas industry


What are microorganisms?

A microorganism or microbe is an organism that is microscopic in size, meaning it is too small to be seen with the naked eye. They exist almost everywhere where there is water, including hot springs, the ocean floor, and deep inside rocks within the Earth's crust. Consequently, they can also be found in crude oil and its derivatives.

There are many kinds of microorganisms, including bacteria, fungi, archaea and protists. As decomposers, they play a vital role in nutrient recycling in ecosystems. However, in the oil and gas industry they pose a threat to safety, product quality and equipment integrity

Why are bacteria present in the oil and gas industry?

Bacteria require the presence of water and a nutrient source. Water and hydrocarbon products co-exist in a number of areas in the oil and gas industry, providing bacteria with the environment they need to proliferate. Aerobic bacteria grow in the presence of oxygen, while anaerobic bacteria (i.e. sulphate-reducing bacteria, or SRB) are found in oxygen-free systems.

Where are bacteria found?

As already mentioned, water and nutrients are key to bacterial growth – and they are present throughout the oil and gas value chain, in tanks, pipelines and other equipment.

Each type of equipment operates under very specific conditions. As inventory turnover in the oil and gas industry is generally high, tanks are typically well aerated (with a high concentration of dissolved oxygen), and aerobic bacteria can thrive. However, dead-ends, pipelines and even equipment with laminar flow can offer advantageous environments for anaerobic bacteria (i.e. SRB, which generate H2S) since there is little or no dissolved oxygen.

But where does the water come from?

Water can be found in air in the form of moisture, it can be introduced into the system through raw materials or crude oil, or it can be left over after cleaning – to highlight just a few of many potential sources.

Water is present throughout the entire oil and gas value chain. For example, crude oil at the production stage (i.e. before it is sent to a refinery), generally contains some water (e.g. 0.5% (w/w)). Refined products, such as diesel, may be blended with up to 7% biodiesel (Vol) in line with the current DIN EN 590 standard. This stipulates that up to 200 mg/kg water is permissible in B7 diesel. This may not seem a high volume in absolute terms, but for bacteria and other microorganisms, this is a huge quantity.

What about yeasts and moulds?

Yeasts and moulds, just like bacteria, require water and a nutrient source. They can be found, for instance, in storage tanks at the interface between oil and water. In combination with bacteria, they can form large masses, known as biofilms or sludge, causing problems such as clogged filters and pipelines.

Size of bacteria

Size of bacteria compared to human hair

growth rate

Reproduction rate of microbes


The consequences of microorganisms for the oil and gas industry


Bacteria stuck on smooth surface - the start of biofim formation (Source: Prof. Dr. Fleming, University-GH Essen)


Pipe blocked with biofilm


Microorganisms can threaten safety and have a negative impact on product quality and equipment integrity at all stages of the oil and gas industry – upstream, midstream and downstream. 


  • Safety issues due to the generation of hydrogen sulphide (oil and gas souring): Learn more about SRB
  1. Air containing hydrogen sulphide in concentrations of between 4.3% and 46% is explosive.
  2. H2S is especially dangerous because it impairs the sense of smell at lower concentrations (100 ppm to 200 ppm).
  • Degradation of equipment integrity:
  1. Biofilms can cause microbiologically influenced corrosion (MIC) of equipment, piping and storage tanks/
  2. Biofilms can result in blocking or plugging of pipelines, heat exchangers, fuel filters and more
  3. Scaling through iron sulphide and carbonates can lead to plugging.
  4. Biofilms can plug filtration systems and equipment, such as valves. Learn more about biofilms
  • Lower product quality:
  1. Contamination of hydrocarbon products with H2S can cause oil and gas quality to fail to meet specifications by exceeding thresholds for H2S or through the formation of unacceptable by-products.
  2. Microbial contamination of hydrocarbon products can render diesel quality non-compliant with the oxidation stability requirement (DIN EN 590).
  • Negative impact on crude oil substances / compounds and oilfield chemicals, such as biopolymers. 

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