Chinese company PetroChina Daqing Tamsag leads in Mongolia with its oil exploration and exploitation. Its capacity increased in 2011 and on June 24 2011, agreed with Oil Authority of Mongolia to expand its "Toson Uul XIX" exploitation field. As the result of this agreement, the Government of Mongolia will decide the grant of additional 650 sq.km area for its exploration.The area locates in the Eastern grassland of Mongolia and the area covers few national park and natural reserve land areas.

Sources say that it was supported by the Ministry of Mineral Resources and Energy.

The Mongolian media concerns about failure of PetroChina Daqing Tamsag in environmental recovery works in the past. PetroChina Daqing Tamsag pays 5% royalty on its output. The Mongolian authority is negotiating with the company on the payment due for taxes on the 5.3 million barrels of crude that have been drilled since 1998.