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
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.
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.
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.
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 compared to human hair
Reproduction rate of microbes
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.