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Wellbore BioChemistry Root cause 7 of 7

Microbial Corrosion in Oil Wells: Causes, Costs and the Remedy

Microbes are blamed for about 20% of corrosion failures. Under their slime, acids and sulfide pit casing, tubing and rods from underneath.

What it is and what it costs

Bacteria that pit steel from underneath

Corroded tubing with a hole and the pitted inside of a pipe
From the biology
What it is
Bacterial slime that eats steel from underneath.
What causes it
Under biofilm, sulfide from SRB and organic acids from acid-producing bacteria eat small, deep pits, and deposits hide them until a failure.
Lifting costs: the usual fixes and why they repeat
Inhibitors and biocides that can’t reach the steel under the slime, plus replacing corroded tubing and rods.
Profitability
Every leak or parted string means a pulling job and days of lost production.
  • $1.372 billion a year: the cost of corrosion in U.S. oil and gas production, including $463 million for downhole tubing.

What this does to a well’s life: Lifting Costs and Well Life

NACE corrosion cost study (AMPP).

Bio slime

A team of bacteria that protects itself

Slime is biofilm: microbes glued to a surface inside a matrix they make themselves. Each layer does a different job.

  1. Where it meets airSulfur-oxidizing bacteria (SOB)Turn H₂S into sulfur and sulfuric acid, which can drive pH to 1 or below, and regenerate sulfate for the SRB. They live in tank roofs and vapor spaces, gun barrels, pits and vents.
  2. Top of the slimeSlime formersBuild the slime and use up the oxygen, so the bottom stays oxygen-free even when the water around it is not.
  3. MiddleAcid-producing bacteria (APB)Turn oil compounds into organic acids that attack steel and feed the SRB.
  4. Against the steelSulfate-reducing bacteria (SRB)Give off H₂S and deposit iron sulfide. The black crust conducts electricity, and the steel under it corrodes into deep pits.
  5. BelowSteelCasing, tubing, rods and tanks: pitted where the deposits sit.
>90%of slime is the matrix, not the cells: polysaccharides, proteins and DNA, mostly water
~1,000×more resistant to biocides for cells in slime than for free-floating cells, so problems come back after biocide jobs
~20%of corrosion failures are blamed on microbes, and up to 40% of internal pipeline corrosion

Testing can mislead. Water samples count free-floating bacteria, but the ones in slime usually matter most.

Not all slime is harmful. Research shows some biofilms protect steel and others attack it, depending on the species.

The remedy

What ChainBreaker does about corrosion

ChainBreaker loosens biofilm and the deposits that shelter it, and competes with acid- and sulfide-making bacteria for surfaces and food, so less acid and sulfide reach the steel.

BioActive reports its microbes also make polysaccharides that coat tubing and rods with a film that guards against corrosion, as a corrosion inhibitor does. With the paraffin removed, the film can reach the metal.

In an Eastern Kansas waterflood, tubing that used to last 8 to 12 months came out “nice and shiny” after more than three years (case study).

Keep the safeguards. Keep corrosion monitoring and inhibitors until your data shows a sustained improvement.

Start with a Production Pilot How ChainBreaker works

Sources for this section