Chinese government decided to introduce production sharing contract (PSC), a popular international model in oil industry worldwide, to tap its offshore hydrocarbon resources in 1982. CNOOC was correspondingly incorporated, authorized under the Regulations of the People's Republic of China on the Exploitation of Offshore Petroleum Resources in Cooperation with Foreign Enterprises, to assume the overall responsibilities for the exploitation of oil and gas resources offshore China in cooperation with foreign partners.

On 16 February 1982, China issued the notification of the first round of bidding for the exploitation of offshore petroleum resources in cooperation with foreign enterprises. CNOOC successively made announcements of bidding notifications on the geophysical exploration in 43 blocks including the north part of the South Yellow Sea geophysical exploration area, the Pearl River Mouth Basin geophysical exploration area, the southern part of the South Yellow Sea geophysical exploration area, the west part of Hainan Island geophysical exploration area and so on. In total 41 corporations from 11 countries participated in the bidding. At the end of 1983, the first round of bidding was successfully conducted, resulting in 18 petroleum contracts signed with 27 petroleum corporations from 9 countries.

Along with the progress of cooperation with overseas partners, in November 1984, January 1987 and June 1992, the second, third and fourth round of offshore oil biddings were successively conducted during the periods when Qin Wencai, Zhong Yiming and Wang Yan served as presidents of CNOOC, respectively. Since then, CNOOC has begun to issue each year the notification of bidding on the exploitation of offshore petroleum resources in cooperation with foreign enterprises.

With the development of CNOOC's cooperation with overseas partners, petroleum exploration discoveries in several Chinese sea areas have been made and many new offshore oil and gas fields have been steadily built up.

In the sea area of the eastern part of the South China Sea, Agip, Chevron and Texaco petroleum corporations discovered Huizhou 33-1 oilfield and Wenchang 19-1 a small oilfield in the first instance; in 1985 Phillips Co. discovered Xijiang 24-3 oilfield and subsequently Xijiang 24-1 oilfield, Xijiang 30-2 oilfield; in 1985 Agip, Chevron and Texaco discovered Huizhou 21-1, 26-1, 32-2 and 32-3 oilfields in Huizhou Sag; several Japanese petroleum corporations discovered Lufeng 13-1 oilfield; in February 1987 Amoco Corporation discovered Liuhua 11-1 oilfield; in May 1989 Occidental discovered Lufeng 22-1 oilfield. These oilfields were successively put into production in 1990-1997, making the production of CNOOC Nanhai East Corporation rise sharply, with oil production reaching 12.97 million tons in 1997. Up to the end of 1997, in the eastern regions of the South China Sea, 24 oilfields and hydrocarbon-bearing structures were discovered.

In the western sea area of the South China Sea, ARCO Petroleum Corporation discovered Ya 13-1 gas field, which was put into production in 1996 to supply gas for Hong Kong and Hainan. CNOOC Nanhai West Corporation cooperated with Total Corporation to explore and develop Weizhou 10-3 oilfield in June 1986.

The exploration in the Bohai Sea areas was relatively patchy. Early in the eighties of the twentieth century, Japanese Petroleum Corporation, Total and ELF carried out exploration in the Bohai Sea with very great investment but small gains and finally without any large breakthrough. As a result, some foreign corporations withdrew from the contract areas.

Considering the geologic conditions of the overland oilfields around Bohai, CNOOC's geologic specialists changed their thinking from an oil search based on abyssal fault to shallow fault. In the contract block from which BP Corporation withdrew on the expiration of the contract, CNOOC conducted a drilling test and discovered Qinhuangdao 32-6 oilfield in 1995, and this discovery greatly shocked foreign corporations. They began to re-examine their bases for previous exploration, schemes, generalized experiences and lessons. Phillips Petroleum Corporation thus discovered Penglai 19-3 a large oilfield in the middle part of Bohai Bay in 1999.

Up to the end of year 2006, CNOOC had signed 182 petroleum contracts and agreements with more than 76 petroleum corporations from 21 countries and regions. Out of the 50 oilfields in production offshore China, 27 were cooperation oilfields jointly developed with partners in 2006.