**Exhibit 99.1**

 

**AMENDED FORM 51-101F2**

**REPORT ONRESERVES DATA BY**

**INTERNALQUALIFIED RESERVES EVALUATOR**

** **

To the Board of Directors of Nexen Inc. (the “Company”):

 

1.                                       Company staff and I have evaluated the Company’sreserves data as at December 31, 2008. The reserves data consist of thefollowing:

 

(a)                                  proved oil and gas reserve quantities estimatedas at last day of the Company’s  mostrecently completed financial year using constant prices and costs; and

 

(b)                                 the related standardized measure.

 

(both (a) and (b) form part of the “FAS 69 Disclosures aboutOil and Gas Producing Activities” contained in the Company’s SupplementaryFinancial Information in its Annual Report on Form 10-K).

 

2.                                       The reserves data have been prepared inaccordance with:

 

(a)                                  United States’ Securities and ExchangeCommission (SEC) requirements;

 

(b)                                 generally accepted industry practices in the United States; and

 

(c)                                  the standards of the Canadian Oil and Gas Evaluation Handbookmodified to the extent necessary to reflect SEC requirements.

 

(collectively, the Nexen Reserves Standards).

 

3.                                       The reserves data are the responsibility of theCompany’s management. My responsibility is to express an opinion whether theevaluation was carried out in accordance with the Nexen Reserves Standards.

 

4.                                       I am not****independent ofthe Company, within the meaning of the term “independent” under NationalInstrument 51-101.

 

5.                                       Among other things, with respect to mattersregarding royalties, operating costs, development plans and costs, abandonmentplans and costs, and income taxes (where applicable), I have placed reasonablereliance on the information and decisions of others in their areas ofauthority, responsibility and expertise within the Company.

 

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6.                                       In my opinion, the reserves data has, in allmaterial respects, been prepared in accordance with the Nexen ReservesStandards.

 

7.                                       Reserves are estimates only and not exactquantities. Estimates of economically recoverable oil and natural gas reservesand future net cash flows are based on a number of variable factors,assumptions and judgements regarding future events. It is believed that thefactors and assumptions used and judgements made in estimating reserves arereasonable based on the information available at the time the estimates wereprepared.  Actual results will vary andsuch variances could be material. However, any variations should be consistentwith the fact that reserves are categorized according to the probability oftheir recovery.

 

8.                                       I have no responsibility to update this opinionfor events and circumstances occurring after the date of this opinion.

 

9.                                       I have signed this Form F2 in my capacityas an employee of Nexen Inc. and not in my personal capacity.

 

 
| /s/ Ian McDonald                           |   |
|--------------------------------------------|--------|
| **Ian McDonald**                           |   |
| **Nexen Inc.**                             |   |
| **Internal Qualified Reserves  Evaluator** |   |
| **Calgary, Alberta**                       |   |
|                                       |   |
| **February 11, 2009**                 |   |

 

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