JINAN, Dec. 25 (Xinhua) -- Oil production in a nature reserve in east China's Shandong Province, was no longer visible this winter. Instead, flocks of birds flying freely over the waters can be espied in the area.

"By the end of November, the oil production equipment in this part of the oil field had all been dismantled," said Deng Zigang with the oil production center of Sinopec Shengli Oilfield.

According to Deng, there were 115 oil production wells with an annual production of 160,000 tonnes in the region. But, the production has been ceased as part of an environmental protection plan. An ecological restoration plan has now been rolled out.

Located in the Yellow River delta, the Shengli Oilfield was discovered in 1961 and developed over the years, while in 1992, the Yellow River delta national nature reserve was established. However, the oil field overlapped with some areas of the nature reserve.

In 2017, environment monitoring groups sent by the central authorities noted that the reserve was a major wetland in Shandong and appropriate action should be taken to deal with the problem of some areas being taken over for oil production.

The oil field immediately decided to withdraw the oil production equipment from the core area and buffer zone of the nature reserve, where no production work should be allowed according to laws and regulations.

The oil field has put in plenty of effort. Besides dismantling equipment in areas that do not allow production, the best equipment has been used in areas that allow oil production. For example, a new kind of material has been used in the pipelines to avoid collision and oil leakage.

The oil field has also invested nearly 60 million yuan (about 9.17 million U.S. dollars) to upgrade the production facilities and eliminate oil spill risks and production pollution.

"As China continues to attach greater importance to the ecological environment in the Yellow River delta, we have been increasingly cautious in oil production," said Su Jianfeng, who has been working at the oil field for more than a decade.

"We replace the pipelines on a regular basis, and work according to environmental protection standards higher than normal," Su said.

It is estimated that after the dismantling, the annual crude oil production of the oil field will drop by about 300,000 tonnes, which means an annual loss of over 550 million yuan.

More than 6 million birds feed and inhabit in the nature reserve during the migration season. So far, 368 species of birds have been spotted in the reserve.