"The weak global economy has provided Chinese companies with a great opportunity to buy foreign assets, allowing many to expand their overseas businesses."
Wang Yilin, the chairman of CNOOC, added that the company had acquired "a leading international platform" through the acquisition of Nexen.
He said: "We strongly believe that this acquisition is a good strategic fit for us and will create long-term value for our shareholders."
Nexen currently has 68 blocks including existing and exploration projects in the North Sea region, making it the second-largest oil producer in the area.
Besides the Buzzard oilfield, of which Nexen owns 43.2 percent of the operational rights, it also has 36.5 percent of the Golden Eagle oilfield about 69 km off the Scottish city of Aberdeen, the biggest proven reserves after Buzzard, which officials believe will contribute greatly to the sustainable output growth of the company's operations in the region.
Meanwhile, in Nigeria Nexen has 20 percent shares of large two offshore oilfields - Usan and Usan West - which both started production in 2012 with good cash flow and profitability so far.
Usan is close to the Akpo oil block of which CNOOC already owns 45 percent of the rights.
"The assets of CNOOC and Nexen complement each other, well," said Li Fanrong, the CEO of CNOOC, and the person appointed chairman of Nexen's new board of directors.
He said he believes the deal has provided a solid platform for CNOOC to expand its businesses across North America.
The company said that Kevin Reinhart, who had been serving as interim CEO of Nexen since January 2012, will remain in charge of the company.
"We want to keep all the current management staff and employees after the acquisition because they are among the most valuable assets of the company.
"Integration after the transaction will also be key to creating full value from the deal," he said.
CNOOC has been developing both domestic and overseas businesses over the past 30 years.
The company has signed about 200 cooperation agreements with 55 countries since 1982, helping it muster rich foreign experience.
With assets now in Asia, Africa, Australia and America, the company is gradually expanding its energy interests from traditional resources to unconventional resources including liquified natural gas, shale oil, shale gas and oil sands.
Through the Nexen deal, CNOOC will gain control of the massive Syncrude oil sands project in Canada, which has already been in production for 34 years.
In addition, the Chinese company will gain high-quality shale gas blocks covering 300,000 acres in Canada, a hugely significant asset for a country which already owns largest shale gas reserves but which is thirsty for acquiring share gas exploration know-how.
However, Yang said this does not mean that CNOOC will shift its shale gas development focus from China to foreign countries.
China's 'leftover women' phenomenon arouses heated debate in West