Underground storage and technical facilities
Microorganisms can cause serious damage in underground storage tanks and technical systems, which can lead to the shutdown of operations. Colonization of system components, e.g. cooling systems, heat exchangers, filters or pipelines, often results in costly maintenance work.
We offer you specially adapted microbiological tests under practical conditions for samples containing water, oil or solids from technical systems, boreholes, probes, caverns and pore or aquifer storage facilities.
Services:
- Extraction of liquid samples or solids from the corresponding geological structures or plant components
- Examination of the samples for all relevant microorganism groups
- Examination of the microorganisms for the utilization of relevant substances, e.g. hydrogen, and for the formation of critical metabolic products, e.g. hydrogen sulphide
- Determination of the degree of colonization and activity under the respective site conditions (salinity, temperature, chemistry, pressure)
- Identification of individual bacterial groups in the microorganism spectra found using molecular biological and biochemical methods
- Determination of the causes of microbial colonization and derivation of possible countermeasures
- Recommendations for stabilizing drilling fluids or brine, checking the effectiveness of biocides used
- Leak tests using microbiological and geochemical analyses (soil gas measurement)
- Expert opinions, risk assessment, scientific studies
Various microbial processes (e.g. sulphate reduction, anaerobic fermentation or polymer formation) can be of significance for the operation of storage facilities or geothermal plants, as a result of which material conversions, corrosion, acidification, permeability losses and probe blockages can occur.
Typical technical accidents caused by microorganisms:
- Degradation or alteration of stored products by microbial processes (degradation of hydrocarbons, e.g. ethylene, methane)
- Quality loss by generation of hydrogen sulphide, methane or carbon dioxide
- Microbially influenced corrosion (MIC) at pipelines, technical installations or sheet pile walls
- Plugging at wellbore bottomhole or surface installations, e.g. at filters or heat exchangers by microbial products (FeS) or biofilms
- Foam production or precipitation
- Collapse of drilling mud or other chemicals of drilling
The tests always require a microbiological analysis of the specific site conditions. Special, tried and tested test media and analysis methods guarantee reliable analysis and typing of the organisms present. In addition, growth tests enable a user-oriented, extensive characterization of the detected bacterial populations. These analyses are supplemented by molecular biological detection and typing methods.
One focus of the future-oriented work will be the evaluation and risk assessment of the underground storage of regeneratively produced hydrogen.
Case histories
Filter blockages on a geothermal system
Due to unexpected, critical pressure increases in the circuit of a geothermal plant, the material of a pump pre-filter was examined microbiologically. High levels of hydrogen-utilizing, sulphate-reducing bacteria (SRB) were detected in liquid cultures and by PCR. Growth tests with the enriched bacterial cultures proved that the organisms only multiply at temperatures below 40°C and therefore cannot originate from the heating circuit, which is over 55°C warm. Instead, they were bacteria introduced from the cold water circuit.
The risk of the organisms adapting to higher temperatures and the associated contamination of the warm water circuit was pointed out and suggestions for further measures were provided.
Stabilisation of drilling fluid for a drilled shaft
A drilled shaft with a 6 m diameter for a salt mine was to be sunk using a CMC drilling fluid (carboxy-methyl cellulose). Several 1,000 m³ of drilling fluid was stored in over ground basins. An intensive microbial CMC disintegration set in during the summer months. As a result, the drilling fluid could not be stabilized even through continuously high subsequent doses of CMC. The driller threatened to remain stuck due to the swelling clay in the drilled hole.
The result of extensive biocide tests showed that in the short term no preparation could be provided for this dimension.
Therefore an alkaline stabilisation of the drilled fluid was tested and suggested at a pH value of 11-12. The bacteria were thus effectively destroyed and the drill could be lowered safely without any further loss of fluid.
Investigations during solution mining for gas storage
During a solution mining process for underground gas storage a heavy precipitation and flocculation with subsequent plugging occurred.
In water samples high cell numbers of various physiological groups of bacteria were detected. It was supposed that organic compounds (cellulosic substances), which have been injected with water into cavern serve as nutrient source. Microbial degradation processes obviously resulted in a high contamination, which has not been suppressed by high salt content of produced brine. Rather, it was demonstrated that during the solution mining process a salt resistant bacteria population established, which could grow on 245 g NaCl per litre.
It could be proven that slime-forming microorganisms were substantially involved in flocculation. As this process continues in simulated tests net-like structures developed containing filamentous bacteria. With increasing salt concentrations more complex filaments were produced. This correlation could be explained with emergence of new bacterial cell morphologies characterized by reduced mobility and disturbed cell division under physiological stress at high salinity.
As a result of microbiological investigations case-specific measures were recommended to reduce nutrient discharge and finally suppress bacteria.
Investigation of corrosion effects on a pipeline
Corrosion damages on the outer wall of a natural gas pipeline within a swampy area have been detected by the operator. The pipeline was equipped with a cathodic corrosion protection.
A key factor for corrosion was initial process of hydrogen sulfide generation by sulfate reducing bacteria (SRB) which utilized the hydrogen jacket as energy source generated by cathodic corrosion protection. Hydrogen sulfide (H2S) produced by SRB reacted with iron ions dissolving from pipeline wall finally forming black iron sulfide (FeS). H2S and FeS are oxidized by several groups of sulfur oxidizing bacteria (SOB) to sulfuric acid and iron(II) sulfate. Specifically Acidithiobacillusferrooxidans oxidizes iron(II) sulfate to iron(III) salts. Starting from iron(II)sulfide (pyrite) substantial amounts of sulfuric acids will be produced in connection with water, which finally lead to an increased microbially influenced corrosion (MIC) of metal components.
As a result of extensive microbiological investigations, the activity of bacteria involved and cause of the corrosion process have been determined.