**Exhibit        8.1**

| Name                      of entity                                              |   | Our                      interest |   | Jurisdiction                      of incorporation |   |
|----------------------------------------------------------------------------------|--------|-----------------------------------|--------|----------------------------------------------------|--------|
| CNOOC                    China Limited                                           |   | 100%                              |   | Tianjin,                    PRC               |   |
| CNOOC                    International Limited                                   |   | 100%                              |   | British                    Virgin Islands     |   |
| China                    Offshore Oil (Singapore) International Pte., Ltd.  |   | 100%                              |   | Singapore                                     |   |
| CNOOC                    Finance (2002) Limited                                  |   | 100%                              |   | British                    Virgin Islands     |   |
| CNOOC                    Finance (2003) Limited                                  |   | 100%                              |   | British                    Virgin Islands     |   |
| CNOOC                    Finance (2004) Limited                                  |   | 100%                              |   | British                    Virgin Islands     |   |
| Malacca                    Petroleum Limited                                     |   | 100%                              |   | Bermuda                                       |
| OOGC                    America, Inc.                                            |   | 100%                              |   | Delaware,                    USA              |
| OOGC                    Malacca Limited                                          |   | 100%                              |   | Bermuda                                       |
| CNOOC                    Southeast Asia Limited                                  |   | 100%                              |   | Bermuda                                       |
| CNOOC                    Africa Holding Limited                                  |   | 100%                              |   | British                    Virgin Islands     |
| CNOOC                    Africa Limited                                          |   | 100%                              |   | British                    Virgin Islands     |
| CNOOC                    Africa (UK) Limited                                     |   | 100%                              |   | London,                    U.K.               |
| CNOOC                    ONWJ Ltd.                                               |   | 100%                              |   | Labuan,                    F.T.,Malaysia      |
| CNOOC                    SES Ltd.                                                |   | 100%                              |   | Labuan,                    F.T.,Malaysia      |
| CNOOC                    Poleng Ltd.                                             |   | 100%                              |   | Labuan,                    F.T.,Malaysia      |
| CNOOC                    Madura Ltd.                                             |   | 100%                              |   | Labuan,                    F.T.,Malaysia      |
| CNOOC                    Blora Ltd.                                              |   | 100%                              |   | Labuan,                    F.T.,Malaysia      |
| CNOOC                    NWS Private Limited                                     |   | 100%                              |   | Singapore                                     |

----

| CNOOC                    Wiriagar Holding Limited                      |   | 100%   |   | British                    Virgin Islands       |
|-----------------------------------------------------------------------------|--------|--------|--------|-------------------------------------------------|
| CNOOC                    Wiriagar Overseas Ltd.                             |   | 100%   |   | British                    Virgin Islands  |
| CNOOC                    Muturi Holding Limited                        |   | 100%   |   | British                    Virgin Islands       |
| CNOOC                    Muturi Ltd.                                        |   | 100%   |   | The                    Isle of Man         |
| CNOOC                    Morocco Limited                                    |   | 100%   |   | Cayman                    Islands          |
| CNOOC                    Canada Limited                                     |   | 100%   |   | British                    Virgin Islands  |
| CNOOC                    Belgium BVBA                                       |   | 100%   |   | Belgium                                    |
| CNOOC                    Australia Limited                                  |   | 100%   |   | British                    Virgin Islands  |
| CNOOC                    Exploration & Production Nigeria Limited  |   | 100%   |   | Nigeria                                    |
| AERD                    PROJECTS NIGERIA Limited                       |   | 92.11% |   | Nigeria                                    |
| CNOOC                    Hong Kong Holding Limited                     |   | 100%   |   | Hong                    Kong                    |
| CNOOC                    Myanmar Holding Limited                       |   | 100%   |   | British                    Virgin Islands       |
| CNOOC                    Myanmar Limited                                    |   | 100%   |   | British                    Virgin Islands  |
| CNOOC                    Caspian (Kazakhstan) Limited                       |   | 100%   |   | Cayman                    Islands               |