The gravity of Kirkuk crude has been especially unstable, trade sources said.
Quality checks at the Turkish port of Ceyhan showed the API degrees of gravity of 20 out of 21 Kirkuk crude cargoes were between 31.14 and 32.41 in one month to late-May, with one at 33.51.
These cargoes were shipped to the US, Morocco, Italy, Turkey, Greece and Italy.
“The gravity of Kirkuk has been unstable. It was lighter in the beginning of March and April. A few cargoes were loaded at API above 34,” a European trader said. “Now it is back around 31-32.”
Crude oils with larger API gravity figures are lighter.
Basra Light, which is exported to Asia from the Iraq oil terminal of Basra, is also becoming heavier.
“The average API last month was between 29-30. I believe it was around 31-32 a year ago,” one Asian buyer said.
The International Crude Oil, Market Handbook in 2007 by Energy Intelligence showed the API gravities of Kirkuk as 35.8 and Basra Light as 34.4.
Traders said sulphur content of Kirkuk has stable around two percent, while that of Basra Light has increased to 3 percent. The handbook in 2007 showed the sulphur content of Basra Light was 2.1 percent.
Iraq’s oil output was around 2.7 million barrels per day, its deputy prime minister Hussain Al-Shahristani said in mid-May.
That accounts for about three percent of global daily oil consumption of 86 million bpd and is larger than the output of fellow OPEC producers Nigeria, the UAE, Kuwait and Venezuela.
Traders attributed the unstable quality of Iraqi crude to blending of fuels from local refining facilities.
“It is a same old story, too much straight run fuel oil,” one trader said.
Iraq started blending fuel oil and some other products to crude oil, mostly Kirkuk, since the late 1990s.
Another trade source said 54,000 bpd of fuel oil was blended into Basra Light in March and 79,000 bpd of fuel oil and natural gasoline into Kirkuk. April and May figures were not available.
“Fuel oil, of course, depresses the quality of the crude,” the source said.
Iraq’s State Oil Marketing Organization (SOMO) was not immediately available to confirm the figures.
Earlier this year, Iraq started exporting oil from the semi autonomous Kurdish region, restarted after a halt since 2009 following the resumption of the Tawke and Taq Taq fields.
The estimated gravity of the oil from Tawke has API gravity of 21 and the oil from Taq Taq has API gravity of 47, Fact Global Energy said.
A trader with an oil company, which buys Iraqi oil for its Mediterranean refinery, said the restart of Taq Taq was thought to make Kirkuk lighter but this has yet to be evident.
Buyers said that they had been given a price escalator and de-escolator — adjusting the price depending on the quality of individual cargoes carrying Kirkuk crude and that complex refineries could absorb the quality fluctuations.
“But obviously, if the quality does not improve, Iraqi crude should become cheaper,” the trader said.