Gas output at Azerbaijan's Shah Deniz field also fell this year, BP said.
ACG output dropped by 2.75% to 58 million barrels in the first quarter, compared with the same period in 2013.
Average production was 645,800 barrels per day, nearly 20,000 bpd below last year's figure.
ACG has been losing production capacity for some years, with BP and Socar trying to stop or reverse the trend.
The
