How microbially influenced corrosion has influenced NCIMB

by NCIMB News

The National Collection of Industrial Food and Marine Bacteria includes more than 10000 environmentally and industrially important bacteria, such as those used in food manufacture or nutrient cycling, as well as a number of species and strains that cause problems for the oil and gas industry, through their role in microbially influenced corrosion and reservoir souring.

Since NCIMB is attending the Reservoir Microbiology Forum this week, we thought we would take a look back at how the work we have done to help the oil and gas industry tackle these problem microbes has influenced the strains held in within our culture collection.

Sulphate reducing bacteria (SRB) are probably the group of microbes that are best known within the oil and gas industry for their role in microbially influenced corrosion and reservoir souring. The existence of these organisms, which grow in the absence of oxygen, can be traced back 3.5 million years and many of them are well suited to the inhospitable conditions found within oilfields.

Many of the sulphate reducing bacteria associated with corrosion are from the genus Desulfovibrio and the early deposits of this genus in the National Collection of Industrial Food and Marine Bacteria include strains isolated from a diverse range of sources, such as the River Thames mud, clay soil from the Netherlands and a brackish lake in Libya.

However, strains deposited in the late 1950s also included those isolated from a corroding cast iron heat exchanger and a corroding gas main as well as oil wells in California and Louisiana.  Moving forward into the 1980s and 1990s, we have strains being deposited that were isolated from untreated seawater as used in secondary recovery of oil from the North Sea Forties field, a soured oil well in Alaska and the severely corroded hull of an oil storage vessel moored off the coast of Indonesia, so we can see the concerns of the oil and gas industry being reflected in the collection through the years. 

Of course, SRB’s are not the only groups of microorganisms involved in oilfield corrosion – other groups of bacteria produce corrosive waste products such as acids and carbon dioxide, and the proliferation of aerobic bacteria can use up oxygen, creating the conditions that favour the anaerobic SRBs.  Consequently, in addition to SRBs, acid producing bacteria and general heterotrphic bacteria (GHB) are also routinely monitored by microbiologists working in this field.

In recent years new molecular techniques have revolutionised our understanding of environmental microbiology and it’s a really exciting time to be working in this field.  Molecular techniques have given microbiologists a better understanding of the microbial ecology of oilfield systems as a whole, as they overcome the requirement for growth in order to identify the organisms present.

However, the more traditional culture based microbiology methods still have an important role to play in monitoring risk of microbially influenced corrosion, not least because of their lower cost compared to molecular methods, and the large quantity of historic data available to inform interpretation of results. 

For more information please contact Michelle Robertson, NCIMB’s Oilfield and Environmental Services Manager.
e: m.robertson@ncimb.com t: 01224 711100