Contaminants
Mercury is our specialism, but it rarely arrives alone. The following are the contaminants we most often survey for, plan around and remove, frequently several of them in the same scope.
Mercury is a naturally occurring element in well fluids from deep geological formations, and is found in oil and gas operations throughout the world. It can be present in natural gas, crude oil, condensate and produced water, as well as in the sludge and solids recovered when cleaning tanks and process vessels.
Pure mercury is the only metal that is liquid at normal temperatures. Like other liquids it gives off vapour as it evaporates, and that vapour is invisible, odourless and toxic. Mercury also combines with other substances to form compounds that can be more toxic than the pure metal, because they help mercury enter the body and travel to critical organs such as the brain, liver and kidneys.
Where it accumulates
Elemental mercury tends to pool or concentrate where the process stream cools, so cryogenic processes and expansions are prime suspects. Mercury reacts with sulphur to form mercuric sulphide, which settles out as a deposit in tanks and pipes, commonly where sweet and sour streams mix. It is also readily adsorbed onto the surface of pipes and vessels, especially where corrosion or sludge has accumulated. This means contamination increases over time even where nothing is visible: inlet pipework, heat exchangers and separators are therefore likely places for mercury to be found.
How we deal with it
Confirming the presence and form of mercury requires careful sampling and access to a competent laboratory. THIS combines survey and analysis with proprietary desorption chemistry and containment methods, then verifies clearance using handheld XRF and mercury vapour analysers.
NORM is Naturally Occurring Radioactive Material. TENORM is Technologically-Enhanced Naturally Occurring Radioactive Material: naturally occurring radioactive material that has been disturbed or altered from its natural setting by human activity, which may result in a relative increase in radiation exposure and risk above background levels.
“Technologically enhanced” means the physical, chemical and radiological properties and concentrations have been altered such that there is potential for redistribution and contamination of environmental media (soil, water and air), increased environmental mobility in soils and groundwater, incorporation of elevated radioactivity into products and construction materials, or improper disposal resulting in unnecessary exposure.
All raw materials contain traces of natural radioactivity. Industries where enhancement takes place receive increasing attention from regulators. The governing principle of radiation protection is to keep doses As Low As Reasonably Achievable, social and economic factors taken into account.
In oil and gas operations, NORM typically presents as radium-bearing scale and sludge in production tubing, separators, water-handling equipment and storage tanks.
Benzene is a colourless, flammable liquid with a sweet odour. It is volatile and evaporates quickly, is formed by both natural processes and human activity, and ranks among the top 20 chemicals produced worldwide.
The two routes of exposure are inhalation and skin absorption. Because liquid benzene evaporates quickly, skin absorption is less common and inhalation of contaminated air is the primary route. Workers in industries that make or use benzene (oil refineries, chemical plants and gasoline-related industries) may be exposed to high levels.
Benzene is considered a human carcinogen on both experimental and epidemiological grounds. NIOSH and OSHA limit occupational exposure to 1 ppm over an average workday and recommend personal protective equipment including respirators.
Hydrocarbon decontamination covers vapour-space and process-stream residues in tanks, towers, columns and piping, and is routinely combined with mercury work to reduce shutdown and turnaround duration.
Pyrophoric iron sulphide (FeS) forms when hydrogen sulphide or other sulphur compounds react with iron oxide on the internal surfaces of vessels, tanks and pipework in sour service. It is stable while the system remains closed and oxygen-free.
On opening a system for entry, inspection or hot work, FeS oxidises rapidly in air. The reaction is strongly exothermic and can raise deposits to ignition temperature within moments, providing an ignition source in an atmosphere that may still contain flammable vapour.
Control depends on keeping deposits wet, chemically oxidising them under controlled conditions, or suppressing them with vapour-suppression chemistry before the system is opened, not on ventilation alone. THIS treats FeS as part of the same pre-entry sequence as mercury and hydrocarbon removal.
Inorganic scale, typically barium, strontium or calcium sulphate and carbonate, deposits inside production tubing, separators, heat exchangers and water-handling systems as pressure, temperature and water chemistry change through the process.
Scale matters for two reasons. It restricts flow and heat transfer, and it concentrates other contaminants: radium co-precipitates with barium sulphate to produce NORM scale, and mercury is readily adsorbed onto scale and sludge surfaces.
Removal is therefore a combined mechanical, chemical and radiological problem, and the arisings must be classified before disposal rather than after.
Legacy aqueous film-forming foams (AFFF) used in platform, terminal and tank-farm fire systems contain per- and polyfluoroalkyl substances (PFAS), persistent compounds that do not break down in the environment and that migrate readily into groundwater.
Replacing a foam stock is only part of the task. PFAS remains adsorbed to the internal surfaces of bladder tanks, proportioners, ring mains and hose reels, and will re-contaminate a fresh fluorine-free charge unless the system is properly cleaned and verified.
Work therefore covers system survey and sampling, controlled drain-down and capture of legacy foam, decontamination of the distribution system, and routing of concentrate and rinsate to appropriately licensed destruction, not to general drainage.
Arsenic is an element widely distributed in the earth’s crust. Elemental arsenic is ordinarily a steel-grey metal-like material. When found in the environment combined with oxygen, chlorine or sulphur it is called inorganic arsenic; combined with carbon and hydrogen it is organic arsenic. The distinction matters because organic forms are usually less harmful than inorganic forms.
Most inorganic and organic arsenic compounds are white or colourless powders that do not break down. They have no smell and most have no taste, so it is difficult to tell if arsenic is present without analysis.
Inorganic arsenic has been recognised as a human poison since ancient times. Long-term oral exposure produces a characteristic pattern of skin changes including darkening and the development of small ‘corns’ or warts on the palms, soles and torso.
In gas processing, arsenic appears alongside mercury as a volatile species and can poison catalyst beds, which makes it a shared concern for both process performance and decontamination planning.
Paraffin wax drops out of crude and condensate as temperature falls below the wax appearance point, building deposits in flowlines, risers, separators and storage tanks and progressively restricting throughput.
For decontamination work, wax is significant because it traps and shields other contaminants. Mercury, NORM scale and hydrocarbon residues held within a wax matrix will not respond to surface treatment and will not be detected by a surface survey until the wax is removed.
Wax dissolution and sludge breaking are therefore normally the first stage of a combined clean, not a separate job.
Hydrogen sulphide is a poisonous, flammable, colourless gas with a characteristic odour of rotten eggs. Most people can smell it at concentrations between 0.0005 and 0.3 ppm, but at high concentrations a person may lose the ability to smell it altogether, which makes it very dangerous.
It occurs both naturally and from industrial processes: in gases from volcanoes, sulphur springs, undersea vents and stagnant water, and in crude petroleum and natural gas. Industrial sources include refineries, natural gas plants, petrochemical plants and coke oven plants.
Hydrogen sulphide enters the body primarily through inhalation but is also absorbed through the skin. Low concentrations irritate the eyes, nose and throat. Brief exposure above 500 ppm can cause loss of consciousness, and in many individuals produces long-term effects including headaches, poor attention span, poor memory and impaired motor function. Fatalities have been reported in sewers, waste dumps, sludge plants, drilling sites, tanks and cesspools.
THIS applies scavenging and suppression chemistry to remove H₂S and mercaptans from gas, water, crude and fuel oils, converting hydrogen sulphide to a stable non-hazardous sulphate salt.
Stagnant produced water, ballast tanks, potable and service water systems and long-idle process equipment support microbial growth, including sulphate-reducing bacteria (SRB), which drive microbially influenced corrosion and generate hydrogen sulphide in situ.
Idle and cold-stacked assets are the common case: a facility shut down for months returns with biofilm, SRB colonies and a souring problem that did not exist at shutdown.
Treatment covers survey and sampling, biocide selection and dosing appropriate to the system and its discharge route, mechanical removal of biofilm and sludge, and verification before the system is returned to service.
Asbestos is the name of a group of highly fibrous minerals with separable, long, thin fibres. The fibres are strong, flexible and heat resistant, which made them useful for many industrial purposes. Because of their durability, asbestos fibres that reach lung tissue remain for long periods.
Researchers have not determined a safe level of exposure, but the greater and longer the exposure, the greater the risk of contracting an asbestos-related disease. People occupationally exposed to asbestos have developed several life-threatening diseases including lung cancer.
Regulatory agencies recognise six asbestos minerals: chrysotile, a serpentine mineral with long flexible fibres, and five amphiboles: actinolite, tremolite, anthophyllite, crocidolite and amosite.
Asbestos is dangerous only when broken crystal fibres become airborne after being disturbed. On older offshore and onshore facilities it is commonly found as acoustic and thermal insulation, fireproofing, gaskets, and roofing and flooring materials, which makes it a routine consideration in demolition and decommissioning scopes.
Tell us what you need decontaminated.
Send us the asset, the contaminant and the constraint. We will tell you what is achievable, where it can be done, and what compliance evidence you will get at the end of it.