MIC and oilfield souring: QuantArray technology

Microbial induced corrosion (MIC) and oilfield souring are complex processes that depend on the actions and interactions of diverse bacterial communities of not only sulfate reducing bacteria but also acid producing bacteria, methanogens, iron oxidizers, slime formers, denitrifiers, and sulfur oxidizing bacteria.

Traditional cultivation-based methods like plate counts, MPNs, and biological activity response tests may vastly underestimate and oversimplify the potential for MIC and souring activity.

The QuantArray is a molecular microbiological method (MMM) that provides accurate and simultaneous quantification of key organisms and functional genes involved in MIC and oilfield souring for more comprehensive assessment of:

• The potential for MIC.
• The effectiveness of treatments and O&M measures.
• Oilfield souring and control efforts.

Sulfate Reduction

Sulfate reducing microorganisms consume hydrogen, produce hydrogen sulfide, and are commonly implicated in pitting corrosion. The MIC QuantArray targets functional genes in sulfate reducing bacteria and sulfate reducing archaea to evaluate the potential for MIC.

Methanogens

Although often overlooked, methanogens utilize hydrogen for growth, contribute to cathodic depolarization, and have been shown to cause corrosion rates comparable to those of sulfate reducing bacteria.

Iron and Mmanganese oxidising bacteria

Iron and manganese oxidising bacteria utilise reduced metals as an energy source producing metal oxide deposits and tubercle formation.

Acid producing bacteria (fermenters and acetogens)

Organic acid production by fermenters and acetogens supports growth of other MIC associated microoganisms and can lead to localized drop in pH. Acetic acid exacerbates carbon dioxide corrosion.

Slime production

Quantification Deinococcus and Meiothermus spp. often considered primary biofilm formers and a functional gene involved in exopolysaccharide (EPS) slime formation by some Burkholderia spp.

Iron reducing bacteria

Iron reducing bacteria reduce insoluble ferric iron to soluble ferrous iron potentially facilitating the removal of protective corrosion products.

Nitrogen cycle - Denitrification, ammonia oxidation, nitrogen fixation

Simultaneous quantification of functional genes involved in key steps in the nitrogen cycle including nitrate reduction, ammonia oxidation, and nitrogen fixation. QuantArray results can be used to assess the effectiveness of nitrate addition in combating MIC and reservoir souring.

Sulfur oxidising bacteria

Often aerobic bacteria oxidise sulfide or elemental sulfur producing sulfuric acid and are commonly implicated in the corrosion of concrete.

Edited from source by Elizabeth Corner

Read the article online at: https://www.oilfieldtechnology.com/drilling-and-production/21052014/mic_and_oilfield_souring_quantarray_technology/