RIO DE JANEIRO - Cooperation between China and Brazil in the petroleum sector has been lifted to a new level, as Chinese financial services are playing an increasingly important role in the South American country's energy industry.

The first five months of 2015 witnessed fast growth of oil trade between the two countries, as Brazil's oil exports to China increased three-fold compared to the same period last year, making China the largest consumer of Brazilian oil in the world.

Brazil exported 5.4 million tons of oil to China from January to May, accounting for 35 percent of Brazil's total oil exports in the same period, according to the Brazilian Ministry of Development, Industry and Foreign Trade.

China Petrochemical Corp (Sinopec), China's second-largest oil and gas producer, won Brazil's Gasene gas pipeline construction project in 2004, pioneering cooperation in the petroleum field between the two countries.

Eleven years later, more Chinese energy companies have entered this South American country, and cooperation has expanded to various fields including oil exploration and technology research, trade of petrochemical equipment and products.

In addition to the fast increasing oil trade, China also upgraded its role in Brazil's oil industry from petroleum pipelines builder to an important investor and partner in exploration of pre-salt oil.

Brazil is an emerging energy superpower. The pre-salt oil reserves found in the waters of its southeastern part in 2007 were estimated to be as much as 70 billion barrels.

Till now, all the four largest Chinese oil companies have entered the pre-salt oil market, mainly through acquisitions.

In 2010, Sinopec invested $7.1 billion in the Brazilian unit of Spain's oil giant Repsol YPF SA. The Chinese company also bought 30 percent stake in Portugal's Gal operations in Brazil.

In 2010, Sinochem Group, China's fourth-largest oil company, paid a total of $3.07 billion for 40 percent of the Peregrino field in Brazil from Statoil, a Norway-headquartered international energy company.

Three years later, Sinochem bought 35 percent of the stake of the Block BC-10 in Campos Basin from Petrobras at the price of $1.43 billion, which further consolidated Sinochem's presence in Brazil.