Oilfield & fuel biocides
We have developed biocides that comply with diverse regulatory and technical requirements for a variety of upstream, midstream and downstream applications. Our biocides have a broad spectrum of antimicrobial activity, combating bacteria, yeasts and moulds. They are highly effective, enabling low dosage levels for cost efficient treatment. Moreover, we offer solutions for modern diesel fuels. Our grotamar® product range is designed to protect diesel and diesel blends from microbial contamination – in fuel tanks and storage facilities, in engines in boats, ships and trucks, and in refineries.
Highly contaminated fuels can be treated with a shock dose of grotamar® to prevent further microbial growth, fuel quality degradation, and microbiologically influenced corrosion (MIC). Continuous and proactive treatment with grotamar® is recommended to prevent fuel contamination.
Challenges that our biocides deal with:
- Providing complete protection against H2S for multiphase systems
- Ensuring efficacy across a wide temperature range, from sub-zero (high viscosity/poor pumpability) to up to 350°C (thermostability)
- Meeting diverse needs for free/low water content for various applications
- Fate of the reaction products (post-addition)
- Efficient H2S scavenging with conventional products generally requires a surplus of H2S scavenger
Biofilms in oil and gas exploration
Bacteria can be planktonic, i.e. free-floating, or sessile, i.e. attached to surfaces as a biofilm. Tests of water samples taken to evaluate bacterial concentrations only detect planktonic cells. A biofilm is an aggregate of microorganisms that adhere to each other and/or to a surface. A biofilm is often referred to as slime; however, not everything described as slime is a biofilm. The microbes produce a matrix of extracellular polymeric substances (EPS) generally comprising extracellular DNA, proteins and polysaccharides. Once established, biofilms are very difficult to remove entirely, and any residual cells can quickly regenerate the colony.
Biofilms in fuel tanks
Water forms condensation in tanks, and this creates droplets on the walls and in pipelines, and accumulates at the tank bottom. These droplets contain microbes, which can metabolise nutrients and generate a slick substance visible as bio sludge in the tank. In severe cases, a slimy biofilm can build on the tank walls. Within this gel-like mass, the microbes are shielded, and can proliferate unchecked. If part of the biofilm breaks off and falls into the diesel, the fuel will be inevitably contaminated. Even a small amount of biofilm contains countless microbes that can derive nutrients for growth from diesel. It is therefore crucial to regularly inspect tanks, and evaluate the need for cleaning.
The only way to remove a biofilm is mechanically, i.e. by means of a thorough tank cleaning. Biocides of all types are only effective against bacteria and moulds on the surface of biofilms – they are unable to penetrate further. As a result, microbes within the biofilm are protected, and can continue to grow even after biocide treatment.A reactive approach to biofilms is insufficient – and even dangerous. Microbes can cause severe corrosion in a very short time, attacking both steel and aluminium. Pitting corrosion is a widespread problem found, for example, on ships – and can result in fuel tank leaks.
By microorganism bacteria, yeasts and moulds are meant. These microorganisms or in colloquial language microbes, are present everywhere. They are in the air, in the soil, in the water and also on our skin. They are not always a problem and some of them are even very useful, e.g. in the food industry. Only the total amount of the microbes might cause a problem in the fuel tank. Under optimal conditions, the microbes double within 20 minutes. After additional 20 minutes, there are 4 then 8 -16 32 – 64 … After 10 hours there are 1 073 741 824 microorganisms. The rapid proliferation explains the enormous build-up of so-called bio sludge in contaminated fuel tanks. This bio sludge blocks the fuel filter more and more and prevents a good flow. The flow of the fuel might stop completely and no fuel can reach the engine.
What are optimal conditions for the proliferation of microbes?
Microbes need water. Water is the source of life! They also need food and warmth to feel comfortable. As we also know, microbes can adapt very well to new living conditions. They have learned how to extract the nutrition they need out of the diesel fuel. With the addition of biodiesel in the fuel it is even easier for microbes to exploit the fuel as food since biofuel is very biodegradable. The temperature in the tank is given and often cannot be influenced, i.e. when a storage tank is outside.
But where is the water coming from?
Diesel fuel contains up to 7% bio-diesel according to the latest DIN EN 590 norm. According to the specification, up to 200 mg/kg water is allowed. 200mg/kg is not a large amount of water, but considering the size of a bacteria or yeast of only some µm, the small amount of water in the tank is the size of a huge lake. The “lake” already provides very good living conditions . Diesel fuel itself can bind up to 60 mg/kg water which means it is not available for microbes. But the remaining 140 mg/kg water is available for microbes. Taking condensation water into account, the lake slowly becomes an ocean. In the past when diesel did not contain a bio component, the water was more inclined to sink to the bottom of the tank because water is heavier than diesel fuel. So the water could be drained from the lowest point of the tank.
Keeping the tank dry is a good housekeeping method to remove the source for microbes. But nowadays, biodiesel has to be mixed into the fuel to fulfil regulations. Biodiesel can have up to 500 mg/kg water, but it can bind up to 5000 mg/kg water. This is good because large amounts of water are bonded and then not available for microbes. No microbial contamination cases have been reported in 100 % biodiesel. The problem starts when only a certain percentage of biodiesel is mixed into the mineral oil fuel because the small biodiesel amount cannot dissolve all the excess water. In addition, the biodiesel acts like an emulsifier and distributes fine water drops in the fuel. With the addition of biofuels, draining the clear water from the tank bottom has become very difficult.
Bio film formation- Consequences of diesel pest
Water can dissolve in fuel, especially under warm and humid conditions. During cool-down, this water can separate from the fuel and together with condensation from the air the water appears in the tank as condensation water. The condensation water is collected at the tank bottom and also builds up water drops at the tank wall and in the pipelines. Microbes are in this water drops. They are building proteins and make the separation of water and fuel difficult because an emulsion has been formed. Diesel fuel is usually bright yellow and clear but after a while it becomes brownish and turbid. As a result of the metabolism microbes also form a slimy substance which becomes visible as bio sludge in the tank. In very heavy cases build up, slimy bio films at the tank wall can be found. In this gel like bio films the microbes can proliferate without any trouble. If parts of the bio film are falling off the wall into fresh diesel, the new diesel will inevitably be contaminated. Loads of microbes in tiny parts of bio film will find new sources for growth in the fresh diesel. So it is crucial to do a regular tank inspection and tank cleaning.
Bio films can only be removed by mechanically treatment during a systematic tank cleaning. A biocide, no matter which one, would only treat the surface of the bio film against bacteria and moulds. Microbes hiding under the jelly bio film are very well protected against the biocide and therefore can survive the treatment. They can continue to grow in the bio film. But this is not enough! Microbes are able to cause severe corrosion in a very short time. Both steel and aluminium can be attacked by microbes. Pitting corrosion is a wide-spread problem and often found on ships and vessels. The result can be leakage in fuel tanks. Especially tanks with low turnover are at risk for microbial contamination with bio film formation and corrosion. To prevent this it is highly recommended to monitor the hygiene of the tank regularly to detect microbial contamination in time. Do not wait until bio sludge is visible with the naked eye.