Buyers reject several Libyan crude cargoes due to high mercury content: sources

London — Buyers have canceled several Libyan Amna, Abu Attifel and Zueitina crude oil purchases after high mercury levels were detected in the cargoes, sources close to the matter said Jan. 21.

The sources said that the issue had so far only impacted the three grades of Amna, Abu Attifel and Zueitina.

State-owned National Oil Corporation has reoffered some of the January-loading cargoes through an official tender, the sources added.

"Some Amna crude cargos, which load from Ras Lanuf are now being tested in Tripoli to make sure there is no mercury contamination," one source close to the matter said.

Representatives at NOC were not immediately available for comment on the matter, despite several attempts.

Libyan oil production has soared by more than 1 million b/d in the past few months to almost 1.3 million b/d, after the nation's two warring factions -- the UN-backed Government of National Accord and the self-styled Libyan National Army -- agreed a peace deal.

Refinery damage

Mercury is present in virtually all oil and gas in both a chemical and elemental form. But mercury levels can vary widely within reservoirs and geographically too.

High levels of mercury can be very toxic, posing concerns for refiners due to potential damage to refining units.

"We understand that the catalysts of some refining units can be damaged completely by high levels of mercury, and it can also cause a lot of damage to refinery infrastructure," said one source.

The high vapor pressure and density of elemental mercury means it concentrates in light end products such as LPG and naphtha, potentially resulting in off-specification material.

Mercury contamination can also be harmful to the refining process through amalgamation with other metals, and poisoning catalyst units.

One source said that the aging oil infrastructure in Libya could have caused the rise in mercury levels. Mercury from crude oil can also accumulate in processing equipment and in oil storage tanks, when it is not maintained well.

A lot of Libya's crude oil tanks, especially in the eastern ports of Ras Lanuf, have suffered damage from militant attacks since the starts of the civil war in 2011.