Reliability of mercury and arsenic sampling and analysis in the petrochemical and oil industry

Mercury (Hg) and arsenic (As) are naturally occurring and problematic compounds in natural gas and crude oil. They are present at concentration levels varying by several orders of magnitude. In addition to health and environmental problems, Hg catalyses the corrosion of aluminium components, with potentially dramatic consequences in processing plants. For As, high concentrations can cause catalyst poisoning and can also induce toxic solid deposition in surface processes or in pipes. A reliable assessment of the concentrations of these two critical elements in hydrocarbon streams is still necessary to anticipate problems and possibly design a treatment unit.The determination and speciation of these two trace elements from deep reservoirs is a very different approach from that applied in clean rooms. The question of the reliability and representativeness of the sampling carried out on site is predominant compared to the analysis and speciation of mercury and arsenic. Sampling and analysis of trace elements in natural gas and oil are full of potential artefacts. In industry, when looking at routine trace element measurements, it is not uncommon to be wrong by several orders of magnitude. This is due to poor consideration of artefacts, including the risk of false positives due to contamination or false negatives due to the delayed breakthrough effect of trace compounds in a well test.The main objectives of this thesis are to track down potential artefacts during sampling and analysis of mercury and arsenic and to propose improvements during these two steps in order to reliably and representatively assess Hg and As concentrations in petroleum fluids.