China's second-largest oil company, China Petrochemical Corp., otherwise known as Sinopec Group, has entered a purchase deal with Devon Energy Corp. to acquire a one-third stake in five Devon exploratory oil projects in the U.S. for $900 million.

The deal, expected to conclude in the current quarter, effectively raises China's holdings of reserves trapped in shale around the world. The Asian country, recognized as the world's second-largest economy, has been aggressively pursuing and buying global energy sources to feed its fast-growing economy. At the same time, it wants to improve its ability to mine domestic shale deposits. China holds some of the world's biggest shale deposits.

Sinopec International Petroleum Exploration & Production Corp, a unit of Sinopec Group, will pay Devon Energy Corp. $900 million in cash, plus $1.6 billion in future drilling costs, according to a statement from Devon. Some 125 wells are expected drilling this year.

Devon added it expects the entire $1.6 billion carry to be realized by end 2014.

All in all, the deal could be worth as much as $2.5 billion.

Sinopec is the second Chinese firm entering the U.S. oil patch. The first was Cnooc Ltd. which bought stakes in Chesapeake Energy Corp.'s operations in south Texas's oil-rich Eagle Ford shale in 2010 and in shale assets in Colorado and Wyoming in 2011.

But what's common is that China National Petroleum Corp., Sinopec Group and Cnooc Ltd. all work to access technology through partnerships in order to develop its own country's shale reserves, estimated to be larger than those in the U.S.

In April, the U.S. Energy Information Administration said China's shale may hold 1,275 trillion cubic feet of gas, or 12 times the country's conventional natural-gas deposits. This leads to the analysis that China's "technically recoverable" reserves are 50 per cent greater than the 862 trillion cubic feet held by the U.S., the EIA added.

"In these joint ventures, the partner does typically get some education on drilling," Scott Hanold, a Minneapolis-based analyst, said in Bloomberg News.

"The more exposure they get, the better," the BBC quoted Mark Hanson of Morningstar as saying.

The shale agreements also aid cash-rich China to spread its global investments by acquiring control stakes in potentially lucrative assets during a period of global financial instability.

"The idea is to reduce risks from holding financial paper," Amy Myers Jaffe, director of the Baker Institute Energy Forum, said in The Wall Street Journal.

Oklahoma City-based Devon jumped 6.6 per cent to $66.11 at the close in New York.