Reuters reports that BP's output at Azerbaijan's Azeri-Chirag-Guneshli (ACG) fields was down 7 percent in 2012, it said, showing a faster fall than that of total Azeri production in a trend that has drawn criticism from the country's president.
But the British oil major's output rose from the Shah Deniz gas field, the country's biggest.
BP said in a news release on Friday that oil output at ACG was 32.9 million tonnes in 2012, down from 35.4 million tonnes in 2011.
Falling oil production at the ACG oilfields, the biggest in Azerbaijan, has raised concerns in the ex-Soviet republic and prompted President Ilham Aliyev to accuse BP of making "false promises".
Officials at BP and state energy company SOCAR say the geology of the country's main oilfields has fallen short of original expectations and they have cited maintenance and higher safety standards at BP after the Macondo oil spill in the Gulf of Mexico as reasons behind the falls of the past 18 months.
Extending a drop that began in 2011, Azerbaijan's oil and condensate production fell 5.3 percent to 42.98 million tonnes in 2012 from 45.40 million in 2011.
BP said on Friday it exported 282.9 million barrels of oil from the ACG in 2012, down from 291.5 million barrels in 2011. Its export via the Baku-Tbilisi-Ceyhan pipeline declined to 246 million barrels last year from 257.3 million barrels in 2011.
During 2012, the ACG consortium led by BP spent about $725 million in operating expenditure and $2.5 billion in capital expenditure.
In 2013, BP plans about $758 million in operating expenditure while capital spending should be roughly unchanged.
In contrast, natural gas output at the Shah Deniz gas field, also operated by BP, rose in 2012 to 7.73 billion cubic metres (bcm) from 6.67 bcm in 2011.
It also produced 2.0 million tonnes of condensate at Shah Deniz, up from 1.8 million tonnes produced in 2011.
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