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CORROSION CONTROL - MICROBIOLOGICALLY INDUCED

SEA WATER --- RIVER WATER --- GROUND WATER

Weight for weight, the most prolifically used resource in the oil business!
All untreated water from natural sources, and particularly sea water, contains millions of invisible micro-organisms in every litre.

Raw water invariably contains dissolved oxygen which supports the existence of microflora. Since the amount of dissolved oxygen present in sea water is limited, bacteria (and macro-organisms) rapidly consume the available supply and then die by 'suffocation' in closed water filled systems. BUT there is a more insidious and potentially destructive population which does not need oxygen to survive. ANAEROBIC BACTERIA (sulphate reducers) thrive in closed stagnant water systems by extracting oxygen from the dissolved salts which are present in all sea water. Sulphates, phosphates and carbonates of sodium, potassium, calcium and magnesium are all sources of vital oxygen for these adaptive micro-organisms.

As the anaerobes strip oxygen from these dissolved salts, the chemistry of the salts is altered and they pass from their neutral state to form corrosive acidic solutions.

The process continues to generate carbonic, sulphuric and phosphoric acids as long as any water is present to provide the source of hydrogen ions - the basis of all acids.
 
The processes outlined above occur in all stagnant and closed water systems in the absence of deliberate oxygenation (aeration).

The corrosive effects of anaerobic bacteria can be catastrophic:

1. Stimulated (Water Flood) Recovery
Pumping raw sea water into an oil or gas bearing formation rapidly induces an anaerobic aqueous state. The results include souring of the reservoir by contamination with acidic sulphides, corrosion of the casings, wellheads and topside pumps, injectors and hardware.

2. Tubular Jackets
Ballasting with sea water assists in stabilising the structure but acidification by bacteria can rapidly corrode the structure from the inside. Painting is expensive and non-renewable. Float-coating is temporary and impractical. Cathodic protection will not eliminate this form of corrosion indefinitely.

3. Flooded Topside Supports
Hollow members above the tide line may be flooded as a fire safety precaution. They then corrode in just the same way as tubular jackets.
 
4. Floating and Semi-Submersible Oil Storage Structures
Tanks, spars and vessels used as collectors are subject to variable cycles of aqueous ballasting and may suffer severe corrosion induced by anaerobes.
 
5. Concrete Hollow Structures
Bacterially induced acidic corrosion is one of the most destructive forces towards concrete structures.

Many solutions have been proposed to overcome these destructive processes.
PROCEINE BIOCIDES are:-

• effective and inexpensive in eliminating all bacteria from sea water (being less costly to use than aldehyde/quaternary mixtures).
• amphoteric in character (being effective in both acidic and basic solutions).
• low in mammalian toxicity and environmental impact.
• safe to handle, presenting little or no hazard to personnel.
• presented as high active liquids at a choice of as-supplied concentrations or as 100% active solid blocks and sticks, packaged ready for use in water soluble plastic wrapping and rapid deployment snap-on netting.