BEIJING, Aug 12 (Reuters) - China's crude oil production in July fell 8.1 percent from a year ago to the lowest since October 2011 on a daily basis, as low prices limit the incentive to keep some wells operating in the world's fourth-largest oil producer.
Crude output last month was 16.72 million tonnes in July, data from the National Bureau of Statistics showed on Friday. On a daily basis July's production is about 3.94 million barrels per day (bpd), down from June's 4.03 million bpd and the fifth straight month of declines in terms of daily output.
For the first seven months of 2016, production was down 5.1 percent versus the same period last year to 118.35 million tonnes, or about 4.06 million bpd.
Dominant domestic producers PetroChina and Sinopec have both projected output declines this year as many of their fields began to operate at a loss, especially during the first quarter when oil prices sank below $40 a barrel.
Sinopec said in July that their domestic production in the first half of 2016 was down 12.95 percent to 128.38 million barrels, or about 705,000 bpd.
In addition to production that is not viable economically, China is also grappling with aging oil fields that are increasingly running out of oil and gas.
Daqing, China's largest field, which produced first oil in 1960, will decline at a rate of 7.2 percent this year, its fastest pace in the last 20 years, according to consultants Energy Aspects.
Natural gas output last month fell 3.3 percent compared with the year ago period to 10.3 billion cubic meters, though for the first seven months of the year production rose 3.1 percent to 79.4 billion cubic meters, the stats bureau said.
Throughput at China's oil refineries rose 2.5 percent in July from a year earlier to 45.32 million tonnes, or 10.67 million bpd, according to the bureau. That was down from June's runs of 10.97 million bpd.
Crude runs in the January to July period rose 2.5 percent year on year to about 10.69 million bpd, according to the data.
(1 tonne= 7.3 billion barrel for crude oil)
(Reporting by Meng Meng and Florence Tan in SINGAPORE; Editing by Richard Pullin and Christian Schmollinger)