on-site analysis
On-site sampling and analysis
Mercury Sampling & Analysis
In a typical reservoir, mercury is present in a variety of forms, principally metallic Hg (liquid and vapor), HgS (the stable, resistant solid fraction), and sometimes Hg2+ (ionic mercury). Metallic mercury is probably the principal form in the reservoir, with HgS tending to be precipitated during production.
Mercury forms amalgams with other metals, particularly aluminum and has the potential to cause corrosion of welds, cryogenic components, aluminum-based heat exchangers, compressor seals/stems/seats, and pump shafts made from copper alloys.
In the downstream processing of gas and oil, mercury can cause premature failure of catalytic beds. If not monitored and controlled correctly a plant contaminated with mercury can lead not only to worker exposure during planned plant shutdowns but also environmental release.
For fields with a high mercury concentration, it may be necessary to incorporate a mercury removal system into the production/process design. The absorbents used in mercury removal systems typically re- move metallic mercury only. It is for this reason (as well as environmental and operator exposure issues) that some oil companies need to identify what species of mercury are present.
3Phase Reservoir Technology Sdn Bhd uses LECO AMA254 to analyze total mercury in gas & liquid form and mercury speciation. With recent method approvals by the EPA and ASTM, the AMA254 offers a fast, cost-effective alternative to conventional CVAAS or ICP. This unique system combusts various matrices without sample pre-treatment or concentration steps-saving your valuable time.
Total mercury can be calculated from combined measured mercury in hydrocarbon gasses and liquid. Hydrocarbon Gasses– Mercury is trapped from a known volume of gas using a gold sand trap and subsequently determined in the trap using either atomic fluorescence or atomic absorption (e.g. ISO 6978) Hydrocarbon Liquid– Determined by combustion in oxygen and final detection by atomic absorption. This method is based on UOP 938 (and ASTM D6722).
Offshore/Onshore Analysis – Mercury Speciation
- For gases mercury is split between elemental and organic using selective aqueous based absorbers with detection by atomic absorption. The LOD achievable is dependant on the volume of gas sampled. 100L of gas will give a limit of detection of ~ 0.2 µg/m3.
- For hydrocarbon liquids mercury is fractionated (semi-speciation) as follows; Total, Total Soluble, Elemental, Ionic, Insoluble (determination of insoluble’s will need to be carried out onshore)
- For water samples mercury is fractionated (semi-speciation) as follows; Total, Total Soluble, Elemental, Insoluble (determination of insoluble’s will need to be carried out on- shore)