State-owned Chinese oil companies have paid $1.5 billion for a stake in an Angolan oil field and bought a $4.2 billion share in an offshore Mozambique gas field in recent weeks, part of a global spending binge by Beijing to secure foreign oil resources.

Industry monitors estimate Chinese companies like the China National Offshore Oil Co. and Sinopec have spent about $100 billion since the start of 2009 on oil and gas assets in Africa, the Middle East and other producing zones, including the United States, to boost imports as domestic fields are depleted.

Sinopec, for example, paid $1 billion this year for a 50 percent stake in Chesapeake Energy's Mississippi Lime gas and oil field. In a 2012 venture into unconventional drilling technologies, it acquired five Devon Energy assets for $2.2 billion.

The Chinese spent a record $35 billion in 2012 alone on joint ventures and outright purchases.

"China's set to become a major producing country outside its borders," observed Fatih Birol, chief economist with the International Energy Agency, the West's oil watchdog. "A significant part of the increased foreign production comes from merger and acquisition transactions last year."

The IEA, based in Paris, reported in February -- in the first assessment of China's recent foreign oil and gas investments -- that Chinese companies produce more than 1.5 million barrels per day.

That's equivalent to the annual output of the Persian Gulf state of Kuwait.

The IEA estimates Chinese production in Iraq could reach more than 2 million bpd by 2020 and almost 3 million bpd by 2035.

By then, the IAE estimates, Iraq's overall production will be 8 million bpd, with a quarter of that, 2 million bpd, exported to China -- as Baghdad drives to boost it production to 9 million bpd by 2017.

Iraq is currently a relatively minor supplier to China, accounting for about 5 percent of Beijing's imports in 2012, about 275,000 bpd.

But Iraq's been one of the Chinese oilmen's prime targets. CNOOC, Petrochina and the China National Petroleum Corp., are all active there and a surge in sales to China is expected.

The Middle East is China's largest foreign source of oil, with Africa second. With an oil boom in the Gulf of Guinea in West Africa and a gas bonanza emerging in the east, Africa's importance to Beijing is growing fast.

Sinopec, which has overseas assets from Argentina to Australia, announced Monday it is set to pay $1.52 billion for a 10 percent share in Marathon Oil's Block 31 field in the Indian Ocean off Angola, with estimated reserves of 533 million barrels of oil.

The deal is subject to approval by the Chinese and Angolan governments, but that's considered very likely. It would boost Sinopec's stake in Block 31 to 15 percent. It paid just under $1 billion for a 5 percent stake from France's Total in 2011.

CNPC agreed in March to pay $4.21 billion for a 20 percent stake in an offshore gas field operated by Italy's Eni in the Indian Ocean off the West African state of Mozambique, which with northern neighbor Tanzania is the center of a burgeoning gas bonanza.

This is expected to attract other Chinese energy companies because of the direct export route across the Indian Ocean to Asia, shipping lanes that have become strategically important for China's energy and raw material imports from Africa and the Persian Gulf.

Angola, one of Africa's top three producers, supplied Beijing with 620,000 bpd in 2012, with another 260,000 bpd coming from South Sudan and 130,000 bpd from the Democratic Republic of Congo.

The development of the energy industry in East Africa has been delayed by poor infrastructure and inadequate regulation.

China has been building highways, railroads and other infrastructure across Africa in recent years to secure access to oil and minerals, such as copper and uranium, for its resource-hungry economy. Chinese oil companies, funded by Beijing's seemingly unlimited supply of cash, are likely to replicate these projects in Mozambique and Tanzania.

These will likely include a pipeline network and a new port/export terminal complex in Tanzania.

Chinese President Xi Jinping underlined Africa's strategic importance to Beijing by making his first overseas visit to the continent in March, promising $20 billion in loans.