10-K/A

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-K/A

AMENDMENT NO. 1

ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(D) OF

THE SECURITIES EXCHANGE ACT OF 1934

For the year ended December 31, 2009

Commission File Number 1-6702

NEXEN INC.

Incorporated under the Laws of Canada

98-6000202

 (I.R.S. Employer Identification No.)

801 – 7th Avenue S.W.

Calgary, Alberta, Canada T2P 3P7

Telephone: (403) 699-4000

Website: www.nexeninc.com

SECURITIES REGISTERED PURSUANT TO SECTION 12(B) OF THE ACT:

TITLE	EXCHANGE REGISTERED ON
Common shares, no par value	The New York Stock Exchange    The Toronto Stock Exchange
Subordinated Securities, due 2043	The New York Stock Exchange    The Toronto Stock Exchange

SECURITIES REGISTERED PURSUANT TO SECTION 12(G) OF THE ACT: NONE.

Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act.

Yes x  No o

Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Exchange Act.

Yes o  No x 

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days.

Yes x  No o

Indicate by check mark if disclosure of delinquent filers pursuant to Item 405 of Regulation S-K is not contained herein, and will not be contained, to the best of registrant’s knowledge, in definitive proxy or information statements incorporated by reference in Part III of this Form 10-K or any amendment to this Form 10-K. x

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smaller reporting company. See the definitions of “large accelerated filer”, “accelerated filer” and “smaller reporting company” in Rule 12b-2 of the Exchange Act.

Large accelerated filer x  Accelerated filer o  Non-accelerated filer o  Smaller reporting company o

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act).

Yes o  No x

On June 30, 2009, the aggregate market value of the voting shares held by non-affiliates of the registrant was approximately Cdn$13 billion based on the Toronto Stock Exchange closing price on that date. On January 31, 2010, there were 523,285,022 common shares issued and outstanding.

EXPLANATORY NOTE

This Amendment No. 1 on Form 10-K/A (this "Amendment") amends the Annual Report on Form 10-K for the year ended December 31, 2009 filed on February 25, 2010 (the "Original Filing").  Nexen Inc. (the "Company") has filed this Amendment to file the following exhibits (which will replace those filed with the Original Filing):

23.2	Report of Third Party, DeGolyer and MacNaughton (selected United Kingdom properties).
23.3	Report of Third Party, DeGolyer and MacNaughton (selected Yemen properties).
23.4	Report of Third Party, DeGolyer and MacNaughton (selected Nigeria properties).
23.5	Consent of DeGolyer and MacNaughton.
23.6	Report of Third Party, McDaniel & Associates Consultants Ltd. (selected Canadian properties).
23.7	Report of Third Party, McDaniel & Associates Consultants Ltd. (Syncrude).
23.8	Consent of McDaniel & Associates Consultants Ltd.
23.9	Report of Third Party, Ryder Scott Company L.P. (selected Gulf of Mexico properties).
23.10	Consent of Ryder Scott Company L.P.

Other information contained in the Original Filing has not been updated.  Therefore, this Amendment should be read together with other documents that the Company has filed with the Securities and Exchange Commission subsequent to the filing of the Original Filing.  Information in such reports and documents updates and supersedes certain information contained in this Amendment.  The filing of this Amendment shall not be deemed an admission that the Original Filing, when made, included any known, untrue statement of material fact or knowingly omitted to state a material fact necessary to make a statement not misleading.

TABLE OF CONTENTS
	PAGE
Part II. – OTHER INFORMATION
ITEM 15.  EXHIBITS, FINANCIAL STATEMENT SCHEDULES	1
Signatures	2

PART II. — OTHER INFORMATION

ITEM 15. EXHIBITS, FINANCIAL STATEMENT SCHEDULES

EXHIBITS     

The following exhibits are being filed as part of this Annual Report on Form 10-K/A:

23.2	Report of Third Party, DeGolyer and MacNaughton (selected United Kingdom properties).
23.3	Report of Third Party, DeGolyer and MacNaughton (selected Yemen properties).
23.4	Report of Third Party, DeGolyer and MacNaughton (selected Nigeria properties).
23.5	Consent of DeGolyer and MacNaughton.
23.6	Report of Third Party, McDaniel & Associates Consultants Ltd. (selected Canadian properties).
23.7	Report of Third Party, McDaniel & Associates Consultants Ltd. (Syncrude).
23.8	Consent of McDaniel & Associates Consultants Ltd.
23.9	Report of Third Party, Ryder Scott Company L.P. (selected Gulf of Mexico properties).
23.10	Consent of Ryder Scott Company L.P.
31.1	Certification of Chief Executive Officer pursuant to Section 302 of the Sarbanes-Oxley Act of 2002.
31.2	Certification of Chief Financial Officer pursuant to Section 302 of the Sarbanes-Oxley Act of 2002.

1

SIGNATURES

Pursuant to the requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, the Company has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized, on December 15, 2010.

NEXEN INC.
By:	/s/  Marvin F. Romanow
	Marvin F. Romanow
	President, Chief Executive Officer and Director

 2

EX-23.2

EXHIBIT 23.2

DeGolyer and MacNaughton

5001 Spring Valley Road

Suite 800 East

Dallas, Texas 75244

December 15, 2010

Nexen Inc.

801-7th Avenue S.W.

Calgary, AB

T2P 3P7

Attention: Reserves Review Committee of the Board of Directors of Nexen Inc.

Re: DeGolyer and MacNaughton - Report of Third Party for certain United Kingdom properties with interests owned by Nexen Inc.

Ladies and Gentlemen:

Pursuant to your request, we have conducted an independent evaluation of Nexen Inc.’s (Nexen) proved and probable oil, condensate, natural gas liquids (NGL), and natural gas reserves, as of December 31, 2009, for certain fields owned by Nexen in the United Kingdom as shown in Table 1A. Nexen has represented that these properties account for 17 percent on an equivalent barrel basis of its proved reserves as of December 31, 2009, and that its reserves estimates have been prepared in accordance with the United States Securities and Exchange Commission (SEC) definitions. We have reviewed information provided to us by Nexen that it represents to be its estimates of the reserves, as of December 31, 2009, for the same properties as those which we evaluated.

Reserves included herein are expressed as reserves as represented by Nexen. Gross reserves are defined as the total estimated petroleum to be produced from these properties after December 31, 2009. Working interest reserves are defined as that portion of the gross reserves attributable to the interests owned by Nexen after deducting all interests owned by others. Net reserves are defined as working interest reserves after deductions for royalties.

Estimates of oil, condensate, and NGL (collectively, Liquids), and natural gas should be regarded only as estimates that may change as further production history and additional

2

DeGolyer and MacNaughton

information become available. Not only are such reserves estimates based on that information which is currently available, but such estimates are also subject to the uncertainties inherent in the application of judgmental factors in interpreting such information.

Data used in this evaluation were obtained from reviews with Nexen personnel, Nexen files, from records on file with the appropriate regulatory agencies, and from public sources. In the preparation of this report we have relied, without independent verification, upon such information furnished by Nexen with respect to property interests, production from such properties, current costs of operation and development, prices for production, agreements relating to current and future operations and sale of production, and various other information and data that were accepted as represented. Furthermore, if in the course of our examination something came to our attention which brought into question the validity or sufficiency of any of such information or data, we did not rely on such information or data until we had satisfactorily resolved o ur questions relating thereto or had independently verified such information or data. A field examination of the properties was not considered necessary for the purposes of this report.

Methodology and Procedures

The process of estimating reserves requires complex judgments and decision-making based on available geological, geophysical, engineering, and economic data. To estimate the economically recoverable oil and natural gas reserves and related future net cash flows, we consider many factors and make assumptions including:

●   expected reservoir characteristics based on geological, geophysical, and engineering assessments;

●   future production rates based on historical performance and expected future operating and investment activities;

●   future oil and gas prices and quality differentials;

●   assumed effects of regulation by governmental agencies; and

●   future development and operating costs.

Our estimate is prepared using standard geological and engineering methods generally accepted by the petroleum industry, and the reserves definitions and standards required by the United States SEC. Generally accepted methods for estimating reserves include volumetric calculations, material balance techniques, production and pressure decline curve analysis, analogy with similar reservoirs, and reservoir simulation. The

3

DeGolyer and MacNaughton

method or combination of methods used is based on our professional judgment and experience.

Discovered oil and natural gas reserves are generally produced only when they are economically recoverable. As such, oil and gas prices and capital and operating costs have an impact on whether reserves will ultimately be produced. As required by United States SEC rules, reserves represent the quantities that are expected to be economically recoverable using existing prices and costs. Estimates may change substantially as additional data from ongoing development activities and production performance becomes available and as economic conditions impacting oil and gas prices and costs change.

The reserves estimates in this report are based upon 2009 first-of-the-month fiscal average pricing using benchmark pricing. Oil prices are based upon the Forties crude oil benchmark of U.S.$60.62 per barrel and Dated Brent of U.S.$60.85 per barrel, while gas prices are based upon the National Balancing Point benchmark of UK£0.32 per therm. Specific pricing for each field was adjusted for historical quality and transportation cost differentials, and for currency exchange rates. The resulting adjusted price is referred to as the “realized price.” For total proved reserves, the estimated average realized price is US$58.08 per barrel of oil and U.S.$3.57 per thousand cubic feet of gas, based upon a volume weighted average of the properties evaluated. For total probable reserves, the weighted average realized price for pr oved plus probable estimates of oil and gas reserves is U.S.$58.68 per barrel and U.S.$4.35 per thousand cubic feet, respectively.

Generally, operations are subject to various levels of government controls and regulations. These laws and regulations may include matters relating to land tenure, drilling, production practices, environmental protection, marketing and pricing policies, royalties, various taxes and levies including income tax, and foreign trade and investment that are subject to change from time to time. Current legislation is generally a matter of public record, and additional legislation or amendments that will affect reserves or when any such proposals, if enacted, might become effective generally cannot be predicted. Changes in government regulations could affect reserves or related economics. In the regions that are currently being evaluated, we believe we have applied existing regulations appropriately.

Certain properties in which Nexen has an interest are subject to the terms of various profit sharing or joint operating agreements. The terms of these agreements generally allow for working interest participants to be reimbursed for portions of capital costs and operating expenses and to share in the profits. The reimbursements and profit proceeds are converted to a barrel of oil equivalent or standard cubic foot of gas equivalent

4

DeGolyer and MacNaughton

by dividing by product prices to determine the “entitlement reserves.” These entitlement reserves are equivalent in principle to net reserves and are used to calculate an equivalent net share, termed an “entitlement interest.” In this report, Nexen reserves or interest for certain properties subject to these agreements is the entitlement based on Nexen’s working interest.

Nexen Estimates

Nexen has represented that its estimated proved and probable reserves attributable to the evaluated properties are based on United States SEC definitions. It represents that its estimates of the reserves attributable to these properties represent 17 percent of its total company proved reserves and 14 percent of its total company probable reserves on an equivalent barrel basis and are as follows, expressed in thousands of barrels (Mbbl), millions of cubic feet (MMcf) and thousands of barrels of oil equivalent (Mboe):

Nexen’s estimate of Reserves as of December 31, 2009

Select Fields Evaluated by DeGolyer and MacNaughton

United Kingdom Properties
	Liquids		Natural Gas		Oil Equivalent
Nexen Reserves	(Mbbl)		(MMcf)		(Mboe)
Working Interest Reserves (before royalties)
Proved		169,450		17,126		172,304
Probable		158,612		64,032		169,284
Working Interest Reserves (after royalties)
Proved		169,403		17,126		172,257
Probable		158,250		64,032		168,923

Note: Gas is converted to oil equivalent using a factor of 6,000 cubic feet of gas per 1 barrel of oil equivalent.

Reserves Audit Opinion

DeGolyer and MacNaughton has used all data, assumptions, procedures, and methods that it considers necessary to prepare this report.

In our opinion, the information relating to estimated net proved and net probable reserves of oil, condensate, natural gas liquids, and gas contained in this report has been prepared according to the definitions and disclosure guidelines required by the United States SEC within Paragraphs 932-235-50-4, 932-235-50-6, 932-235-50-7, and 932-235-50-9 of the Accounting Standards Update 932-235-50, Extractive Industries – Oil and Gas (Topic

5

DeGolyer and MacNaughton

932): Oil and Gas Reserve Estimation and Disclosures (January 2010) of the Financial Accounting Standards Board and Rules 4–10(a) (1)–(32) of Regulation S–X and Rules 302(b), 1201, and 1202(a) (1), (2), (3), (4), (5), (8) of Regulation S–K of the United States Securities and Exchange Commission.

In comparing the detailed proved and proved-plus-probable reserves estimates prepared by us to those prepared by Nexen, we have found differences, both positive and negative. In our opinion, the proved and proved-plus-probable reserves for the reviewed properties as estimated by Nexen are, in aggregate when compared to our estimates on the basis of equivalent barrels, reasonable because each is within 10 percent of our estimates.

DeGolyer and MacNaughton is an independent petroleum engineering consulting firm that has been providing petroleum consulting services throughout the world for over 70 years. DeGolyer and MacNaughton does not have any financial interest, including stock ownership, in Nexen. Our fees were not contingent on the results of our evaluation. This letter report has been prepared at the request of Nexen.

Submitted,

/s/  DeGOLYER and MacNAUGHTON

DeGOLYER and MacNAUGHTON

Texas Registered Engineering Firm F-716

cc:	Mr. Craig Beattie
	V.P. Technical Assurance
	Nexen International Division
	Mr. Brad Kopas
	Deloitte & Touche LLP

	/s/Lloyd W. Cade, P.E.
[SEAL]	Lloyd W. Cade, P.E.
	Senior Vice President
	DeGolyer and MacNaughton

6

DeGolyer and MacNaughton

TABLE 1A

NEXEN FIELDS EVALUATED by DeGOLYER and MacNAUGHTON

as of

DECEMBER 31, 2009

PROPERTIES	FIELDS
United Kingdom	Buzzard
	Scott
	Telford
	Farragon
	Ettrick
	Golden Eagle Area
	Duart
	Rochelle

EX-23.3

EXHIBIT 23.3

DeGolyer and MacNaughton

5001 Spring Valley Road

Suite 800 East

Dallas, Texas 75244

December 15, 2010

Nexen Inc.

801-7th Avenue S.W.

Calgary, AB

T2P 3P7

Attention: Reserves Review Committee of the Board of Directors of Nexen Inc.

Re: DeGolyer and MacNaughton – Report of Third Party for certain Yemen properties with interests owned by Nexen Inc.

Ladies and Gentlemen:

Pursuant to your request, we have conducted an independent evaluation of Nexen Inc.’s (Nexen) proved and probable oil, condensate, natural gas liquids (NGL), and natural gas reserves, as of December 31, 2009, for certain fields owned by Nexen in Yemen as shown in Table 1A. Nexen has represented that these properties account for 2 percent on an equivalent barrel basis of its proved reserves as of December 31, 2009, and that its reserves estimates have been prepared in accordance with the United States Securities and Exchange Commission (SEC) definitions. We have reviewed information provided to us by Nexen that it represents to be its estimates of the reserves, as of December 31, 2009, for the same properties as those which we evaluated.

Reserves included herein are expressed as reserves as represented by Nexen. Gross reserves are defined as the total estimated petroleum to be produced from these properties after December 31, 2009. Working interest reserves are defined as that portion of the gross reserves attributable to the interests owned by Nexen after deducting all interests owned by others. Net reserves are defined as working interest reserves after deductions for royalties.

Estimates of oil, condensate, and NGL (collectively, Liquids), and natural gas should be regarded only as estimates that may change as further production history and additional

2

DeGolyer and MacNaughton

information become available. Not only are such reserves estimates based on that information which is currently available, but such estimates are also subject to the uncertainties inherent in the application of judgmental factors in interpreting such information.

Data used in this evaluation were obtained from reviews with Nexen personnel, Nexen files, from records on file with the appropriate regulatory agencies, and from public sources. In the preparation of this report we have relied, without independent verification, upon such information furnished by Nexen with respect to property interests, production from such properties, current costs of operation and development, prices for production, agreements relating to current and future operations and sale of production, and various other information and data that were accepted as represented. Furthermore, if in the course of our examination something came to our attention which brought into question the validity or sufficiency of any of such information or data, we did not rely on such information or data until we had satisfactorily resolved o ur questions relating thereto or had independently verified such information or data. A field examination of the properties was not considered necessary for the purposes of this report.

Methodology and Procedures

The process of estimating reserves requires complex judgments and decision-making based on available geological, geophysical, engineering, and economic data. To estimate the economically recoverable oil and natural gas reserves and related future net cash flows, we consider many factors and make assumptions including:

●   expected reservoir characteristics based on geological, geophysical, and engineering assessments;

●   future production rates based on historical performance and expected future operating and investment activities;

●   future oil and gas prices and quality differentials;

●   assumed effects of regulation by governmental agencies; and

●   future development and operating costs.

Our estimate is prepared using standard geological and engineering methods generally accepted by the petroleum industry, and the reserves definitions and standards required by the United States SEC. Generally accepted methods for estimating reserves include volumetric calculations, material balance techniques, production and pressure decline curve analysis, analogy with similar reservoirs, and reservoir simulation. The

3

DeGolyer and MacNaughton

method or combination of methods used is based on our professional judgment and experience.

Discovered oil and natural gas reserves are generally produced only when they are economically recoverable. As such, oil and gas prices and capital and operating costs have an impact on whether reserves will ultimately be produced. As required by United States SEC rules, reserves represent the quantities that are expected to be economically recoverable using existing prices and costs. Estimates may change substantially as additional data from ongoing development activities and production performance becomes available and as economic conditions impacting oil and gas prices and costs change.

The reserves estimates in this report are based upon 2009 first-of-the-month fiscal average pricing using benchmark pricing. Oil price is based upon the Dated Brent crude oil benchmark of U.S.$60.85 per barrel. Specific oil pricing was adjusted for historical quality and transportation cost differentials. The resulting adjusted price is referred to as the “realized price” and is estimated to be U.S.$60.46 per barrel of oil for proved and probable reserves.

Generally, operations are subject to various levels of government controls and regulations. These laws and regulations may include matters relating to land tenure, drilling, production practices, environmental protection, marketing and pricing policies, royalties, various taxes and levies including income tax, and foreign trade and investment that are subject to change from time to time. Current legislation is generally a matter of public record, and additional legislation or amendments that will affect reserves or when any such proposals, if enacted, might become effective generally cannot be predicted. Changes in government regulations could affect reserves or related economics. In the regions that are currently being evaluated, we believe we have applied existing regulations appropriately.

Certain properties in which Nexen has an interest are subject to the terms of various profit sharing or joint operating agreements. The terms of these agreements generally allow for working interest participants to be reimbursed for portions of capital costs and operating expenses and to share in the profits. The reimbursements and profit proceeds are converted to a barrel of oil equivalent or standard cubic foot of gas equivalent by dividing by product prices to determine the “entitlement reserves.” These entitlement reserves are equivalent in principle to net reserves and are used to calculate an equivalent net share, termed an “entitlement interest.” In this report, Nexen reserves or interest for certain properties subject to these agreements is the entitlement based on Nexen’s working interest.

4

DeGolyer and MacNaughton

Nexen Estimates

Nexen has represented that its estimated proved and probable reserves attributable to the evaluated properties are based on United States SEC definitions. It represents that its estimates of the reserves attributable to these properties represent 2 percent of its total company proved reserves and less than 1 percent of its total company probable reserves on an equivalent barrel basis and are as follows, expressed in thousands of barrels (Mbbl), millions of cubic feet (MMcf) and thousands of barrels of oil equivalent (Mboe):

Nexen’s estimate of Reserves as of December 31, 2009

Select Fields Evaluated by DeGolyer and MacNaughton

Yemen Properties
	Liquids		Natural Gas		Oil Equivalent
Nexen Reserves	(Mbbl)		(MMcf)		(Mboe)
Working Interest Reserves (before royalties)
Proved		21,195		0		21,195
Probable		2,575		0		2,575
Working Interest Reserves (after royalties)
Proved		13,258		0		13,258
Probable		1,258		0		1,258

Note: Gas is converted to oil equivalent using a factor of 6,000 cubic feet of gas per 1 barrel of oil equivalent.

Reserves Audit Opinion

DeGolyer and MacNaughton has used all data, assumptions, procedures, and methods that it considers necessary to prepare this report.

In our opinion, the information relating to estimated net proved and net probable reserves of oil, condensate, natural gas liquids, and gas contained in this report has been prepared according to the definitions and disclosure guidelines required by the United States SEC within Paragraphs 932-235-50-4, 932-235-50-6, 932-235-50-7, and 932-235-50-9 of the Accounting Standards Update 932-235-50, Extractive Industries – Oil and Gas (Topic 932): Oil and Gas Reserve Estimation and Disclosures (January 2010) of the Financial Accounting Standards Board and Rules 4–10(a) (1)–(32) of Regulation S–X and Rules 302(b), 1201, and 1202(a) (1), (2), (3), (4), (5), (8) of Regulation S–K of the United States Securities and Exchange Commission.

5

DeGolyer and MacNaughton

In comparing the detailed proved and proved-plus-probable reserves estimates prepared by us to those prepared by Nexen, we have found differences, both positive and negative. In our opinion, the proved and proved-plus-probable reserves for the reviewed properties as estimated by Nexen are, in aggregate when compared to our estimates on the basis of equivalent barrels, reasonable because each is within 10 percent of our estimates.

DeGolyer and MacNaughton is an independent petroleum engineering consulting firm that has been providing petroleum consulting services throughout the world for over 70 years. DeGolyer and MacNaughton does not have any financial interest, including stock ownership, in Nexen. Our fees were not contingent on the results of our evaluation. This letter report has been prepared at the request of Nexen.

Submitted,

/s/ DeGOLYER and MacNAUGHTON

DeGOLYER and MacNAUGHTON

Texas Registered Engineering Firm F-716

cc:	Mr. Craig Beattie
	V.P. Technical Assurance
	Nexen International Division
	Mr. Brad Kopas
	Deloitte & Touche LLP

	/s/Lloyd W. Cade, P.E.
	Lloyd W. Cade, P.E.
[SEAL]	Senior Vice President
	DeGolyer and MacNaughton

DeGolyer and MacNaughton

TABLE 1A

NEXEN FIELDS EVALUATED by DeGOLYER and MacNAUGHTON

as of

DECEMBER 31, 2009

PROPERTIES	FIELDS
Yemen Masila (Block 14)	Bainoon/Naziah
	Camaal
	Dahban
	Dais
	Haru
	Heijah
	Hemiar
	Naar
	North East Camaal
	North Camaal
	North East Sunah
	Qataban
	Raydah
	Ressib
	South Hemiar
	South Ressib
	Sunah
	Tawila
	West Camaal
	West Hemiar

EX-23.4

EXHIBIT 23.4

DeGolyer and MacNaughton

5001 Spring Valley Road

Suite 800 East

Dallas, Texas 75244

December 15, 2010

Nexen Inc.

801-7th Avenue S.W.

Calgary, AB

T2P 3P7

Attention: Reserves Review Committee of the Board of Directors of Nexen Inc.

Re: DeGolyer and MacNaughton - Report of Third Party for certain Nigeria properties with interests owned by Nexen Inc.

Ladies and Gentlemen:

Pursuant to your request, we have conducted an independent evaluation of Nexen Inc.’s (Nexen) proved and probable oil, condensate, natural gas liquids (NGL), and natural gas reserves, as of December 31, 2009, for certain fields owned by Nexen in Nigeria. Nexen has represented that these properties account for less than 5 percent on an equivalent barrel basis of its proved reserves as of December 31, 2009, and that its reserves estimates have been prepared in accordance with the United States Securities and Exchange Commission (SEC) definitions. We have reviewed information provided to us by Nexen that it represents to be its estimates of the reserves, as of December 31, 2009, for the same properties as those which we evaluated.

Reserves included herein are expressed as reserves as represented by Nexen. Gross reserves are defined as the total estimated petroleum to be produced from these properties after December 31, 2009. Working interest reserves are defined as that portion of the gross reserves attributable to the interests owned by Nexen after deducting all interests owned by others. Net reserves are defined as working interest reserves after deductions for royalties.

Estimates of oil, condensate, and NGL (collectively, Liquids), and natural gas should be regarded only as estimates that may change as further production history and additional

2

DeGolyer and MacNaughton

information become available. Not only are such reserves estimates based on that information which is currently available, but such estimates are also subject to the uncertainties inherent in the application of judgmental factors in interpreting such information.

Data used in this evaluation were obtained from reviews with Nexen personnel, Nexen files, from records on file with the appropriate regulatory agencies, and from public sources. In the preparation of this report we have relied, without independent verification, upon such information furnished by Nexen with respect to property interests, production from such properties, current costs of operation and development, prices for production, agreements relating to current and future operations and sale of production, and various other information and data that were accepted as represented. Furthermore, if in the course of our examination something came to our attention which brought into question the validity or sufficiency of any of such information or data, we did not rely on such information or data until we had satisfactorily resolved o ur questions relating thereto or had independently verified such information or data. A field examination of the properties was not considered necessary for the purposes of this report.

Methodology and Procedures

The process of estimating reserves requires complex judgments and decision-making based on available geological, geophysical, engineering, and economic data. To estimate the economically recoverable oil and natural gas reserves and related future net cash flows, we consider many factors and make assumptions including:

●   expected reservoir characteristics based on geological, geophysical, and engineering assessments;

●   future production rates based on historical performance and expected future operating and investment activities;

●   future oil and gas prices and quality differentials;

●   assumed effects of regulation by governmental agencies; and

● future development and operating costs.

Our estimate is prepared using standard geological and engineering methods generally accepted by the petroleum industry, and the reserves definitions and standards required by the United States SEC. Generally accepted methods for estimating reserves include volumetric calculations, material balance techniques, production and pressure decline curve analysis, analogy with similar reservoirs, and reservoir simulation. The

3

DeGolyer and MacNaughton

method or combination of methods used is based on our professional judgment and experience.

Discovered oil and natural gas reserves are generally produced only when they are economically recoverable. As such, oil and gas prices and capital and operating costs have an impact on whether reserves will ultimately be produced. As required by United States SEC rules, reserves represent the quantities that are expected to be economically recoverable using existing prices and costs. Estimates may change substantially as additional data from ongoing development activities and production performance becomes available and as economic conditions impacting oil and gas prices and costs change.

The reserves estimates in this report are based upon 2009 first-of-the-month fiscal average pricing using benchmark pricing. Oil price is based upon the Dated Brent crude oil benchmark of U.S.$60.85 per barrel. Specific oil pricing was adjusted for estimated area quality and transportation cost differentials. The resulting adjusted price is referred to as the “realized price” and is estimated to be U.S.$58.18 per barrel of oil for proved and probable reserves.

Generally, operations are subject to various levels of government controls and regulations. These laws and regulations may include matters relating to land tenure, drilling, production practices, environmental protection, marketing and pricing policies, royalties, various taxes and levies including income tax, and foreign trade and investment that are subject to change from time to time. Current legislation is generally a matter of public record, and additional legislation or amendments that will affect reserves or when any such proposals, if enacted, might become effective generally cannot be predicted. Changes in government regulations could affect reserves or related economics. In the regions that are currently being evaluated, we believe we have applied existing regulations appropriately.

Certain properties in which Nexen has an interest are subject to the terms of various profit sharing or joint operating agreements. The terms of these agreements generally allow for working interest participants to be reimbursed for portions of capital costs and operating expenses and to share in the profits. The reimbursements and profit proceeds are converted to a barrel of oil equivalent or standard cubic foot of gas equivalent by dividing by product prices to determine the “entitlement reserves.” These entitlement reserves are equivalent in principle to net reserves and are used to calculate an equivalent net share, termed an “entitlement interest.” In this report, Nexen reserves or interest for certain properties subject to these agreements is the entitlement based on Nexen’s working interest.

4

DeGolyer and MacNaughton

Nexen Estimates

Nexen has represented that its estimated proved and probable reserves attributable to the evaluated properties are based on United States SEC definitions. It represents that its estimates of the reserves attributable to these properties represent less than 5 percent of its total company proved reserves and less than 5 percent of its total company probable reserves on an equivalent barrel basis. Due to disclosure restrictions required by the Nigerian Government, Nexen’s estimates are not presented herein.

Reserves Audit Opinion

DeGolyer and MacNaughton has used all data, assumptions, procedures, and methods that it considers necessary to prepare this report.

In our opinion, the information relating to estimated net proved and net probable reserves of oil, condensate, natural gas liquids, and gas contained in this report has been prepared according to the definitions and disclosure guidelines required by the United States SEC within Paragraphs 932-235-50-4, 932-235-50-6, 932-235-50-7, and 932-235-50-9 of the Accounting Standards Update 932-235-50, Extractive Industries – Oil and Gas (Topic 932): Oil and Gas Reserve Estimation and Disclosures (January 2010) of the Financial Accounting Standards Board and Rules 4–10(a) (1)–(32) of Regulation S–X and Rules 302(b), 1201, and 1202(a) (1), (2), (3), (4), (5), (8) of Regulation S–K of the United States Securities and Exchange Commission.

In comparing the detailed proved and proved-plus-probable reserves estimates prepared by us to those prepared by Nexen, we have found differences, both positive and negative. In our opinion, the proved and proved-plus-probable reserves for the reviewed properties as estimated by Nexen are, in aggregate when compared to our estimates on the basis of equivalent barrels, reasonable because each is within 10 percent of our estimates.

5

DeGolyer and MacNaughton

DeGolyer and MacNaughton is an independent petroleum engineering consulting firm that has been providing petroleum consulting services throughout the world for over 70 years. DeGolyer and MacNaughton does not have any financial interest, including stock ownership, in Nexen. Our fees were not contingent on the results of our evaluation. This letter report has been prepared at the request of Nexen.

Submitted,

/s/ DeGOLYER and MacNAUGHTON

DeGOLYER and MacNAUGHTON

Texas Registered Engineering Firm F-716

cc:	Mr. Craig Beattie
	V.P. Technical Assurance
	Nexen International Division
	Mr. Brad Kopas
	Deloitte & Touche LLP

	/s/Lloyd W. Cade, P.E.
	Lloyd W. Cade, P.E.
[SEAL]	Senior Vice President
	DeGolyer and MacNaughton

EX-23.5

EXHIBIT 23.5

DeGolyer and MacNaughton

5001 Spring Valley Road

Suite 800 East

Dallas, Texas 75244

December 15, 2010

Nexen Inc.

801-7th Avenue S.W.

Calgary, Alberta T2P 3P7

Board of Directors:

We hereby consent to references to DeGolyer and MacNaughton contained in the section entitled “Basis of Reserves Estimates” within “Reserves, Production and Related Information” as set out in Part I, Items 1&2 Business and Properties of the Annual Report on Form 10-K/A for the year ended December 31, 2009, of Nexen Inc. (the Form 10-K/A) and to the use of our three Report of Third Party letter reports dated December 15, 2010, concerning the United Kingdom, Yemen Masila, and Nigeria, respectively, relating to our evaluation of certain oil and gas properties of Nexen Inc., which are included as exhibits in the Form 10-K/A.

Very truly yours,

/s/ DeGOLYER and MacNAUGHTON

DeGOLYER and MacNAUGHTON

Texas Registered Engineering Firm F-716

EX-23.6

EXHIBIT 23.6

December 15, 2010

Nexen Inc.

801-7th Avenue S.W.

Calgary, AB

T2P 3P7

Attention: Reserves Review Committee of the Board of Directors of Nexen Inc.

Re: McDaniel & Associates - Report of Third Party for certain Canadian properties owned by Nexen Inc., excluding Syncrude

Ladies and Gentlemen:

Pursuant to your request, McDaniel and Associates (“McDaniel”) has conducted an evaluation of Nexen Inc.’s (“Nexen”) proved and probable oil, condensate, natural gas liquids (NGL), natural gas, and synthetic crude oil reserves, as of December 31, 2009, for certain fields owned by Nexen in Canada as shown in Table 1A, which includes Nexen’s Canadian conventional, CBM, and Long Lake properties.  Nexen has represented that these properties account for 39 percent of its total proved reserves (75 percent of its total probable reserves) and 98 percent of the proved reserves (99 percent of its probable reserves) in its Canadian properties excluding Syncrude on an equivalent barrel basis as of December 31, 2009, and that its reserve estimates have been prepared in accordance wit h the United States’ Securities and Exchange Commission (“SEC”) definitions. We have reviewed information provided to us by Nexen that they represent to be its estimate of the reserves, as of December 31, 2009, for the same properties as those which we evaluated.

Reserves included herein are expressed as reserves as represented by Nexen. Gross reserves are defined as the total estimated petroleum to be produced from these properties after December 31, 2009. Working interest reserves are defined as that portion of the gross reserves attributable to the interests owned by Nexen after deducting all working interests owned by others. Net reserves are defined as working interest reserves after the deduction of royalties.

2200, Bow Valley Square 3, 255 - 5 Avenue SW, Calgary AB  T2P 3G6     Tel: (403) 262-5506     Fax: (403) 233-2744     www.mcdan.com

Nexen Inc.	December 15, 2010
Report of Third Party for Canadian Properties, excluding Syncrude	Page 2

Estimates of oil, condensate, NGL (collectively liquids), natural gas and synthetic crude oil should be regarded only as estimates that may change as further production history and additional information become available. Not only are such reserves estimates based on that information which is currently available, but such estimates are also subject to the uncertainties inherent in the application of judgmental factors in interpreting such information.

Data used in this evaluation were obtained from reviews with Nexen personnel, Nexen files, from records on file with the appropriate regulatory agencies, and from public sources. In the preparation of this report we have relied, without independent verification, upon such information furnished by Nexen with respect to property interests, production from such properties, current costs of operation and development, prices for production, agreements relating to current and future operations and sale of production, and various other information and data that were accepted as represented.  Furthermore, if in the course of our examination something came to our attention which brought into question the validity or sufficiency of any of such information or data, we did not rely on such information or data until we had satisfactorily resolved our questions relating thereto or had independently verified such information or data. A field examination of the properties was not considered necessary for the purposes of this report.

Methodology and Procedures

The process of estimating reserves requires complex judgments and decision-making based on available geological, geophysical, engineering and economic data. To estimate the economically recoverable oil, natural gas reserves and synthetic crude oil and related future net cash flows, we consider many factors and make assumptions including:

— expected reservoir characteristics based on geological, geophysical and engineering assessments;

— future production rates based on historical performance and expected future operating and investment activities;

— future oil and gas prices and quality differentials;

— assumed effects of regulation by governmental agencies; and

— future development and operating costs.

Nexen Inc.	December 15, 2010
Report of Third Party for Canadian Properties, excluding Syncrude	Page 3

Our estimates are prepared using standard geological and engineering methods generally accepted by the petroleum industry, and the reserves definitions and standards required by the United States SEC.  Generally accepted methods for estimating reserves include volumetric calculations, material balance techniques, production and pressure decline curve analysis, analogy with similar reservoirs, and reservoir simulation.  The method or combination of methods used is based on our professional judgment and experience.

Discovered oil and natural gas reserves are generally only produced when they are economically recoverable. As such, oil and gas prices, and capital and operating costs have an impact on whether reserves will ultimately be produced. As required by SEC rules, reserves represent the quantities that we expect to economically recover using existing prices and costs. Estimates may change substantially as additional data from ongoing development activities and production performance becomes available and as economic conditions impacting oil and gas prices and costs change.

The reserves estimates in this report are based upon 2009 first-of-the month fiscal average pricing using benchmark pricing. Oil prices are primarily based upon West Texas Intermediate at Cushing crude oil benchmark of US$61.18 per barrel and Western Canadian Select at Hardisty benchmark of Cdn$59.28 per barrel. Gas prices are based upon AECO benchmark of Cdn$3.72 per gigajoule. Specific pricing for each field was adjusted for historical quality and transportation cost differentials, and for currency exchange rates. The resulting adjusted price is referred to as the “realized price”. For total proved reserves, the estimated average realized prices are Cdn$56.74 per barrel of oil, Cdn$67.84 per barrel of synthetic crude oil, and Cdn$3.66 per thousand cubic feet of gas, based upon a volume weighted av erage of the properties evaluated. For total probable reserves, the weighted average realized prices for proved plus probable estimates of reserves are Cdn$56.71 per barrel of oil, Cdn$67.84 per barrel of synthetic crude oil, and Cdn$3.66 per thousand cubic feet of gas.

Generally, operations are subject to various levels of government controls and regulations.  These laws and regulations may include matters relating to land tenure, drilling, production practices, environmental protection, marketing and pricing policies, royalties, various taxes and levies including income tax, and foreign trade and investment, that are subject to change from time to time.  Current legislation is generally a matter of public record, and additional legislation or amendments that will affect reserves or when any such proposals, if enacted, might become effective generally can not be predicted.  Changes in government regulations could affect reserves or related economics.  In the regions that are currently being evaluated we believe we have applied existing regul ations appropriately.

Nexen Inc.	December 15, 2010
Report of Third Party for Canadian Properties, excluding Syncrude	Page 4

Nexen Estimates

Nexen has represented that estimated proved and probable reserves attributable to the evaluated properties are based on SEC definitions. It represents that its estimates of the reserves attributable to these properties represent approximately 39 percent of its total company proved reserves before royalties and approximately 75 percent of its total company probable reserves before royalties on a equivalent basis and are as follows, expressed in thousands of barrels (mbbl), millions of cubic feet (mmcf) and thousands of barrels of oil equivalent (mboe):

Nexen’s estimate of Reserves as of December 31, 2009

Select Canadian Fields Evaluated by McDaniel and Associates

Conventional, CBM, and Long Lake

Nexen Reserves	Synthetic Crude Oil (mboe)	Liquids (mbbl)	Natural Gas (mmcf)	Oil Equivalent (mboe)
Working Interest Reserves (before royalties)
Proved	318,248	32,036	250,708	392,069
Probable	887,412	18,926	73,718	918,624
Working Interest Reserves (after royalties)
Proved	290,761	26,517	231,626	355,882
Probable	753,891	16,135	68,170	781,388

Note: Gas is converted to oil equivalent using a factor of 6,000 cubic feet of gas per 1 barrel of oil equivalent.

Reserves Audit Opinion

McDaniel has used all data, assumptions, procedures and methods that it considers necessary to prepare this report.

In our opinion, the information relating to estimated proved and probable reserves of oil, condensate, natural gas liquids, gas and synthetic crude oil contained in this report has been prepared according to the definitions and disclosure guidelines required by the United States SEC within Paragraphs 932-235-50-4, 932-235-50-6, 932-235-50-7 and 932-235-50-9 of the Accounting Standards Update 932-235-50, Extractive Industries – Oil and Gas (Topic 932): Oil and Gas Reserve Estimation and Disclosures (January 2010) of the Financial Accounting Standards Board and Rules 4–10(a) (1)–(32) of Regulation S–X and Rules 302(b) and 1201, 1202(a) (1), (2), (3), (4), (5), (8) of Regulation S-K of the Securities and Exchange Commission.

Nexen Inc.	December 15, 2010
Report of Third Party for Canadian Properties, excluding Syncrude	Page 5

In comparing the detailed proved and proved plus probable reserves estimates prepared by us to those prepared by Nexen, we have found differences, both positive and negative. In our opinion, the proved and proved plus probable reserves for the reviewed properties as estimated by Nexen are, in aggregate when compared to our estimates on the basis of equivalent barrels, reasonable because each is within 10 percent of our estimates.

The analyses of these properties, as reported herein, were conducted within the context of an audit of a distinct group of properties in aggregate as part of the total corporate level reserves.  Extraction and use of these analyses outside of this context may not be appropriate without supplementary due diligence.

McDaniel is an independent petroleum engineering consulting firm that has been providing petroleum consulting services throughout the world for over 50 years. McDaniel does not have any financial interest, including stock ownership, in Nexen. Our fees were not contingent on the results of our evaluation. This letter report has been prepared at the request of Nexen.

This report was prepared by McDaniel & Associates Consultants Ltd. for the exclusive use of Nexen Inc.  It is not to be reproduced, distributed, or made available, in whole or in part to any person, company, or organization other than Nexen Inc. without the knowledge and consent of McDaniel & Associates Consultants Ltd.  We reserve the right to revise any of the estimates provided herein if any relevant data existing prior to preparation of this report was not made available or if any data provided was found to be erroneous.

If there are any questions, please contact the writer directly at (403) 218-1379.

Sincerely,

McDaniel & Associates Consultants Ltd.

/s/ P. A. Welch

P. A. Welch, P. Eng.

CC:	Mr. David Richardson, P. Eng.
	Canadian Oil and Gas,
	Division Reserves Manager
	Mr. Brad Kopas
	Deloitte & Touche LLP

Nexen Inc.	December 15, 2010
Report of Third Party for Canadian Properties, excluding Syncrude	Page 6

Table 1A

Nexen Fields Evaluated by McDaniel

Canadian Oil and Gas properties, excluding Syncrude

As of December 31, 2009

	BUSINESS UNIT	PROPERTY NAME
1	CBM	CBM - CORBETT
2	CBM	CBM - DORIS
3	CBM	CBM - THUNDER
4	CDN GAS	BALZAC
5	CDN GAS	HATTON
6	CDN GAS	HATTON EAST
7	CDN GAS	MEDICINE HAT
8	HEAVY OIL	CACTUS LAKE
9	HEAVY OIL	COURT
10	HEAVY OIL	MARSDEN
11	HEAVY OIL	SENLAC
12	HEAVY OIL	WINTER
13	LONG LAKE	LONG LAKE Phase 1
14	LONG LAKE	LONG LAKE SOUTH Phase 1

EX-23.7

EXHIBIT 23.7

December 15, 2010

Nexen Inc.

801-7th Avenue S.W.

Calgary, AB

T2P 3P7

Attention: Reserves Review Committee of the Board of Directors of Nexen Inc.

Re: McDaniel & Associates  - Report of Third Party for the Syncrude property owned by Nexen Inc.

Ladies and Gentlemen:

Pursuant to your request, McDaniel and Associates (“McDaniel”) has conducted an audit of Nexen Inc.’s (“Nexen”) proved and probable synthetic crude oil reserves in Syncrude Canada Ltd. (“Syncrude”), as of December 31, 2009.  Nexen has represented that this property accounts for approximately 32 percent of its total proved reserves (4 percent of its total probable reserves) and 100 percent of its proved reserves (100 percent of its proba ble reserves) for its Syncrude ownership on an equivalent barrel basis as of December 31, 2009, and that its reserve estimates have been prepared in accordance with the United States’ Securities and Exchange Commission (“SEC”) definitions.  We have reviewed information provided to us by Nexen that they represent to be its estimate of the reserves, as of December 31, 2009, for the Syncrude property.

Reserves included herein are expressed as reserves as represented by Nexen. Gross reserves are defined as the total estimated petroleum to be produced from these properties after December 31, 2009. Working interest reserves are defined as that portion of the gross reserves attributable to the interests owned by Nexen after deducting all working interests owned by others. Net reserves are defined as working interest reserves after the deduction of royalties.

Estimates of oil, condensate, and NGL (collectively liquids), natural gas and synthetic crude oil should be regarded only as estimates that may change as further production history and additional information become available. Not only are such reserves estimates based on that information which is currently available, but such estimates are also subject to the uncertainties inherent in the application of judgmental factors in interpreting such information.

2200, Bow Valley Square 3, 255 - 5 Avenue SW, Calgary AB  T2P 3G6     Tel: (403) 262-5506     Fax: (403) 233-2744     www.mcdan.com

Nexen Inc.	December 15, 2010
Report of Third Party for Syncrude property	Page 2

Data used in this evaluation were obtained from reviews with Nexen personnel, Nexen files, from records on file with the appropriate regulatory agencies, and from public sources. In the preparation of this report we have relied, without independent verification, upon such information furnished by Nexen with respect to property interests, production from such properties, current costs of operation and development, prices for production, agreements relating to current and future operations and sale of production, and various other information and data tha t were accepted as represented.  Furthermore, if in the course of our examination something came to our attention which brought into question the validity or sufficiency of any of such information or data, we did not rely on such information or data until we had satisfactorily resolved our questions relating thereto or had independently verified such information or data. A field examination of the properties was not considered necessary for the purposes of this report.

Methodology and Procedures

The process of estimating reserves requires complex judgments and decision-making based on available geological, geophysical, engineering and economic data. To estimate the economically recoverable oil, synthetic crude oil and natural gas reserves and related future net cash flows, many factors and make assumptions are considered, including:

— expected reservoir characteristics based on geological, geophysical and engineering assessments;

— future production rates based on historical performance and expected future operating and investment activities;

— future oil and gas prices and quality differentials;

— assumed effects of regulation by governmental agencies; and

— future development and operating costs.

Generally accepted methods for estimating reserves include volumetric calculations, material balance techniques, production and pressure decline curve analysis, analogy with similar reservoirs, and reservoir simulation.

Nexen Inc.	December 15, 2010
Report of Third Party for Syncrude property	Page 3

We have performed our audit by reviewing the estimates, assumptions, supporting working papers and other data underlying the reserves estimate prepared by Nexen. We have audited to the standard geological and engineering methods generally accepted by the petroleum industry, and the reserves definitions and standards required by the United States SEC.  Our assessment of the method or combination of methods used in a reserves estimate is based on our professional judgment and experience.

Discovered oil and natural gas reserves are generally only produced when they are economically recoverable. As such, oil and gas prices, and capital and operating costs have an impact on whether reserves will ultimately be produced. As required by SEC rules, reserves represent the quantities that we expect to economically recover using existing prices and costs. Estimates may change substantially as additional data from ongoing development activities and production performance becomes available and as economic conditions impacting oil and gas prices and costs change.

The reserves estimates in this report are based upon 2009 first-of-the-month fiscal average pricing using benchmark pricing. Syncrude synthetic crude oil price is based upon West Texas Intermediate at Cushing crude oil benchmark of US$61.18 per barrel. Syncrude synthetic crude oil pricing was adjusted for historical quality and transportation cost differentials, and currency exchange rates. The resulting adjusted price is referred to as the “realized price” and is estimated to be Cdn$70.85 per barrel of synthetic crude oil for proved and probable reserves.

Generally, operations are subject to various levels of government controls and regulations.  These laws and regulations may include matters relating to land tenure, drilling, production practices, environmental protection, marketing and pricing policies, royalties, various taxes and levies including income tax, and foreign trade and investment, that are subject to change from time to time.  Current legislation is generally a matter of public record, and additional legislation or amendments that will affect reserves or when any such proposals, if enacted, might become effective generally can not be predicted.  Changes in government regulations could affect reserves or related economics.  In the region that is currently being audited we believe Nexen has applied existing regulat ions appropriately.

Nexen Estimates

Nexen has represented that estimated proved and probable reserves attributable to the evaluated properties are based on SEC definitions. It represents that its estimates of the reserves attributable to this property represent approximately 32 percent of its total company proved reserves before royalties and approximately 4 percent of its total company probable

Nexen Inc.	December 15, 2010
Report of Third Party for Syncrude property	Page 4

reserves before royalties on a equivalent basis and are as follows, expressed in thousands of barrels (mbbl) and thousands of barrels of oil equivalent (mboe):

Nexen’s estimate of Syncrude Reserves as of December 31, 2009

Nexen Reserves	Synthetic Crude Oil (mboe)	Liquids (mbbl)	Natural Gas (mmcf)	Oil Equivalent (mboe)
Working Interest Reserves (before royalties)
Proved	323,935			323,935
Probable	46,326			46,326
Working Interest Reserves (after royalties)
Proved	288,352			288,352
Probable	40,711			40,711

Reserves Audit Opinion

McDaniel has used all data, assumptions, procedures and methods that it considers necessary to prepare this report.

In our opinion, the estimates of proved and probable reserves of synthetic crude oil contained in this report has been prepared according to the definitions and disclosure guidelines required by the United States SEC within Paragraphs 932-235-50-4, 932-235-50-6, 932-235-50-7 and 932-235-50-9 of the Accounting Standards Update 932-235-50, Extractive Industries – Oil and Gas (Topic 932): Oil and Gas Reserve Estimation and Disclosures (January 2010) of the Financial Accounting Standards Board and Rules 4–10(a) (1)–(32) of Regulation S–X and Rules 302(b) and 1201, 1202(a) (1), (2), (3), (4), (5), (8) of Regulation S-K of the Securities and Exchange Commission.

In our opinion, the proved and proved plus probable reserves for the reviewed property as estimated by Nexen are reasonable because if we were to perform our own detailed evaluation of the property we expect the resulting estimates would be within 10% of Nexen’s estimates.

The analysis of this property, as reported herein, was conducted within the context of an audit in aggregate as part of the total corporate level reserves. Extraction and use of this analysis outside of this context may not be appropriate without supplementary due diligence.

McDaniel is an independent petroleum engineering consulting firm that has been providing petroleum consulting services throughout the world for over 50 years. McDaniel does not have any financial interest, including stock ownership, in Nexen. Our fees were not contingent on the results of our audit. This letter report has been prepared at the request of Nexen.

Nexen Inc.	December 15, 2010
Report of Third Party for Syncrude property	Page 5

This report was prepared by McDaniel & Associates Consultants Ltd. for the exclusive use of Nexen Inc.  It is not to be reproduced, distributed, or made available, in whole or in part to any person, company, or organization other than Nexen Inc. without the knowledge and consent of McDaniel & Associates Consultants Ltd.  We reserve the right to revise any of the estimates provided herein if any relevant data existing prior to preparation of this report was not made available or if any data provided was found to be erroneous.

If there are any questions, please contact the writer directly at (403) 218-1378.

Sincerely,

McDaniel & Associates Consultants Ltd.

/s/ B. H. Emslie

B. H. Emslie, P. Eng.

Senior Vice President

CC:	Mr. B Frasson, P. Eng., MBA
	Director – Syncrude Investment
	Mr. Brad Kopas
	Deloitte & Touche LLP

EX-23.8

EXHIBIT 23.8

December 15, 2010

Nexen Inc.

801-7th Avenue S.W.

Calgary, Alberta  T2P 3P7

Board of Directors:

We hereby consent to references to McDaniel & Associates Consultants Ltd. contained in the section entitled “Basis of Reserves Estimates” within “Reserves, Production and Related Information” as set out in Part I, Items 1&2 Business and Properties of the Annual Report on Form 10-K/A for the year ended December 31, 2009, of Nexen Inc. (the Form 10-K/A) and to the use of our two Report of Third Party letter reports dated December 15, 2010, concerning our evaluation of certain Canadian oil and gas properties owned by Nexen Inc. and our audit of Nexen Inc.’s Syncrude property ownership which are included as exhibits in the Form 10-K/A.

Sincerely,

McDaniel & Associates Consultants Ltd.

/s/ P. A. Welch

P. A. Welch, P. Eng.

2200, Bow Valley Square 3, 255 - 5 Avenue SW, Calgary AB  T2P 3G6     Tel: (403) 262-5506     Fax: (403) 233-2744     www.mcdan.com

EX-23.9

EXHIBIT 23.9

December 15, 2010

Nexen Inc.

801-7th Avenue S.W.

Calgary, AB

T2P 3P7

Attention: Reserves Review Committee of the Board of Directors of Nexen Inc.

Re: Ryder Scott Company L.P. – Report of Third Party for certain properties located in the United States Gulf of Mexico with interests owned by Nexen Inc.

Ladies and Gentlemen:

Pursuant to your request, Ryder Scott Company L.P. (“Ryder Scott”) has conducted an independent evaluation of Nexen Inc.’s (“Nexen”) proved and probable oil, natural gas liquids (“NGL”), and gas reserves for certain properties owned by Nexen in the United States Gulf of Mexico Shelf and Deep Water.  The properties evaluated are listed in Table 1A.  Nexen has represented that these properties account for approximately 4.5 percent of its total company proved reserves and 1.9 percent of its total company probable reserves on an equivalent barrel basis as of December 31, 2009, and that its reserve estimates have been prepared in accordance with the United States Securities and Exchange Commission (“SEC”) definitio ns.  We have reviewed information provided to us by Nexen that they represent to be its estimate of the reserves, as of December 31, 2009, for the same properties as those which we evaluated.

The proved and probable reserves included herein are expressed as reserves as represented by Nexen.  Gross reserves are defined as the total estimated petroleum to be produced from these properties after December 31, 2009.  Working interest reserves are defined as that portion of the gross reserves attributable to the interests owned by Nexen after deducting all working interests owned by others.  Net reserves are defined as working interest reserves after the deduction of royalties.

Estimates of oil, condensate, and NGL (collectively “Liquids”), and natural gas reserves should be regarded only as estimates that may change as further production history and additional information become available.  Not only are such reserves estimates based on that information which is currently available, but such estimates are also subject to the uncertainties inherent in the application of judgmental factors in interpreting such information.

Data used in this evaluation were obtained from reviews with Nexen personnel, Nexen files, from records on file with the appropriate regulatory agencies, and from public sources.  In the preparation of this report we have relied, without independent verification, upon such information furnished by Nexen with respect to property interests, production from such properties, current costs of operation and development, prices for production, agreements relating to current and future operations and sale of production, and various other information and data that were accepted as represented.  Furthermore, if in the course of our examination something came to our attention which brought into question the validity or sufficiency of any of such information or data, we did not r ely on such information or data until we had satisfactorily resolved our questions relating thereto or had independently verified such information or data.  A field examination of the properties was not considered necessary for the purposes of this report.

600,  1015   4TH  STREET, S.W.CALGARY, ALBERTA T2R 1J4TEL (403) 262-2799FAX (403) 262-2790

621  17TH STREET, SUITE 1550DENVER, COLORADO 80293-1501TEL (303) 623-9147FAX (303) 623-4258

Nexen, Inc.

December 15, 2010

Page 2

Methodology and Procedures

The process of estimating reserves requires complex judgments and decision-making based on available geological, geophysical, engineering and economic data.  To estimate the economically recoverable oil and natural gas reserves and related future net cash flows, we consider many factors and make assumptions including:

●   reservoir characteristics based on geological, geophysical and engineering assessments;

●   future production rates based on historical performance and expected future operating and investment activities;

●   quality differentials and hydrocarbon prices as required by SEC guidelines;

●   assumed effects of regulation by governmental agencies; and

●   future development and operating costs.

Our estimate is prepared using standard geological and engineering methods generally accepted by the petroleum industry, and the reserves definitions and standards required by the United States SEC.  Generally accepted methods for estimating reserves include volumetric calculations, material balance techniques, production and pressure decline curve analysis, analogy with similar reservoirs, and reservoir simulation.  The method or combination of methods used is based on our professional judgment and experience.

Discovered oil and natural gas reserves are generally only produced when they are economically recoverable.  As such, oil and gas prices, and capital and operating costs have an impact on whether reserves will ultimately be produced.  As required by SEC rules, reserves represent the quantities that we expect to economically recover using existing prices and costs.  Estimates may change substantially as additional data from ongoing development activities and production performance becomes available and as economic conditions impacting oil and gas prices and costs change.

The reserves estimates in this report are based upon 2009 first-of-the month fiscal average pricing using benchmark pricing. Oil prices are based upon the West Texas Intermediate at Cushing crude oil benchmark of US$61.18 per barrel, while gas prices are based upon the Henry Hub benchmark of US$3.82 per mmbtu. Specific pricing for each field was adjusted for historical quality and transportation cost differentials. The resulting adjusted price is referred to as the “realized price.” For total proved reserves, the estimated average realized price is US$57.14 per barrel of oil and US$3.97 per thousand cubic feet of gas, based upon a volume weighted average of the properties evaluated. For total probable reserves, the weighted average realized price for prove d plus probable estimates of oil and gas reserves is US$56.93 per barrel and US$3.97 per thousand cubic feet, respectively.

Generally, operations are subject to various levels of government controls and regulations.  These laws and regulations may include matters relating to land tenure, drilling, production practices, environmental protection, marketing and pricing policies, royalties, various taxes and levies including income tax, and foreign trade and investment, that are subject to change from time to time.  Current legislation is generally a matter of public record, and additional legislation or amendments that will affect reserves or when any such proposals, if enacted, might become effective generally can not be predicted.  Changes in government regulations could affect reserves or related economics.  In the regions that are currently being evaluated we believe w e have applied existing regulations appropriately.

RYDER SCOTT COMPANY   PETROLEUM CONSULTANTS

Nexen, Inc.

December 15, 2010

Page 3

Nexen Estimates

Nexen has represented that estimated proved and probable reserves attributable to the evaluated properties are based on SEC definitions.  It represents that its estimates of the reserves attributable to these properties represent 4.5 percent of its total company proved reserves and 1.9 percent of its total company probable reserves on a equivalent basis are as follows, expressed in thousands of barrels (mbbl), millions of cubic feet (mmcf) and thousands of barrels of oil equivalent (mboe):

Nexen’s Estimate of Reserves as of December 31, 2009

Selected Gulf of Mexico Properties Evaluated by Ryder Scott Company L.P.

	Liquids	Gas	BOE
	(mbbl)	(mmcf)	(mboe)
Working Interest (before royalty)
Total Proved	18,178	167,015	46,013
Total Probable	6,625	99,022	23,128
Working Interest (after royalty)
Total Proved	16,175	145,876	40,488
Total Probable	5,848	84,704	19,965

Note:   Natural Gas is converted to oil equivalent using a factor of 6,000 cubic feet of gas per 1 barrel of oil equivalent.

Reserves Audit Opinion

At Nexen’s request, we have compared the proved and probable reserves independently evaluated by us to the reserves prepared by Nexen according to the definitions and disclosure guidelines required by the United States SEC contained in the Securities and Exchange Commission Title 17, Code of Federal Regulations, Modernization of Oil and Gas Reporting, released January 14, 2009 in the Federal Register (“SEC definitions”) and the Accounting Standards Update 2010-3 Amendments to Topic 932 (“ASU Topic 932”) published by the Financial Accounting Standards Board (“FASB”) in the FASB Accounting Standards Codification.

In our opinion, the estimated reserves prepared by Nexen referred to above for the properties reviewed comply with the SEC definitions and ASU Topic 932.  In comparing the detailed proved and proved plus probable reserves evaluated by us to those prepared by Nexen, we have found differences, both positive and negative.  In our opinion, the proved and proved plus probable reserves for the reviewed properties as estimated by Nexen are, in aggregate, when compared to our estimates on the basis of equivalent barrels, reasonable because each is within 10 percent of our estimates.

Ryder Scott has used all data, assumptions, procedures and methods that it considers necessary to prepare this report.  Ryder Scott is an independent petroleum engineering consulting firm that has been providing petroleum consulting services throughout the world for over seventy years.  Ryder Scott does not have any financial interest, including stock ownership, in Nexen.  Our fees were not contingent on the results of our evaluation.

RYDER SCOTT COMPANY   PETROLEUM CONSULTANTS

Nexen, Inc.

December 15, 2010

Page 4

The professional qualifications for Mr. Richard J. Savoie, the technical person primarily responsible for estimating and auditing the reserves information discussed in this letter report, are included as an attachment to this letter.

This letter report has been prepared at the request of Nexen.

Sincerely,
RYDER SCOTT COMPANY L.P. TBPE Firm Registration No. F-1580
\s\ Richard J. Savoie
Richard J. Savoie, P. E. TBPE License No. 40538 Senior Vice President
	[SEAL]

cc:           Mr. Steve Aeschbach,

Reserves Manager,

Nexen Petroleum U.S.A. Inc.

Mr. Brad Kopas

Deloitte & Touche LLP

RYDER SCOTT COMPANY   PETROLEUM CONSULTANTS

Nexen, Inc.

December 15, 2010

Page 5

Table 1A

Nexen Fields Evaluated by Ryder Scott Company L.P.

United States: Gulf of Mexico properties

As of December 31, 2009

Shelf Properties
Eugene Island 18	South Marsh Island 257
Eugene Island 255-57-58	Vermilion 76
Eugene Island 259	Vermilion 302/321
Eugene Island 295	Vermilion 339/340
High Island 582	West Cameron 170
Cote de Mer

Deep Water Properties
Aspen	Knotty Head
Dawson	Longhorn
Garden Banks 205	Gunnison
Mississippi Canyon 72	Green Canyon 50
Green Canyon 6	Tobago
Green Canyon 137	Wrigley

RYDER SCOTT COMPANY   PETROLEUM CONSULTANTS

Professional Qualifications of Primary Technical Person

The conclusions presented in this report are the result of technical analysis conducted by teams of geoscientists and engineers from Ryder Scott Company, L.P.  Mr. Richard J. Savoie is the primary technical person responsible for the estimate of the reserves, future production, and income presented herein.

Mr. Savoie, an employee of Ryder Scott Company L.P. (Ryder Scott) since 1997, is a Senior Vice President and also serves as an Engineering Group Coordinator responsible for coordinating and supervising staff and consulting engineers of the company in ongoing reservoir evaluation studies worldwide.  Before joining Ryder Scott, Mr. Savoie served in a number of engineering positions with Shell Oil Company, Union Texas Petroleum, Kaneb Operating Company, Ltd., Amax Oil and Gas, Inc., and Amerac Energy Corporation.  For more information regarding Mr. Savoie’s geographic and job specific experience, please refer to the Ryder Scott Company website at

http://www.ryderscott.com/Experience/Employees.php.

Mr. Savoie earned a Bachelor of Science degree in Petroleum Engineering from Louisiana State University in 1968 and is a licensed Professional Engineer in the State of Texas.  He is also a member of the Society of Petroleum Engineers.

In addition to gaining experience and competency through prior work experience, the Texas Board of Professional Engineers requires a minimum of fifteen hours of continuing education annually, including at least one hour in the area of professional ethics, which Mr. Savoie fulfills.  As part of his 2009 continuing education hours, Mr. Savoie attended an internally presented eighthours of formalized training as well as a day long public forum relating to the definitions and disclosure guidelines contained in the United States Securities and Exchange Commission Title 17, Code of Federal Regulations, Modernization of Oil and Gas Reporting, Final Rule released January 14, 2009 in the Federal Register.  Mr. Savoie attended an additional twenty-five hours of for malized in-house training as well as an additional twenty two hours of formalized external training during 2009 covering such topics as the SPE/WPC/AAPG/SPEE Petroleum Resources Management System, reservoir engineering, geoscience and petroleum economics evaluation methods, procedures and software and ethics for consultants.

Based on his educational background, professional training and more than forty years of practical experience in the estimation and evaluation of petroleum reserves, Mr. Savoie has attained the professional qualifications as a Reserves Estimator and Reserves Auditor set forth in Article III of the “Standards Pertaining to the Estimating and Auditing of Oil and Gas Reserves Information” promulgated by the Society of Petroleum Engineers as of February 19, 2007.

RYDER SCOTT COMPANY   PETROLEUM CONSULTANTS

EX-23.10

EXHIBIT 23.10

December 15, 2010

We hereby consent to references to Ryder Scott Company L.P. contained in the section entitled “Basis of Reserves Estimates” within “Reserves, Production and Related Information” as set out in Part I, Items 1&2 Business and Properties of the Annual Report on Form 10-K/A for the year ended December 31, 2009, of Nexen Inc. (the Form 10-K/A) and to the use of our Report of Third Party letter report dated December 15, 2010, concerningour evaluation of certain oil and gas properties of Nexen Inc. located in the United States Gulf of Mexico, which are included as exhibits in the Form 10-K/A.

\s\ Ryder Scott Company, L..P.

RYDER SCOTT COMPANY, L.P.

TBPE Firm Registration No. F-1580

600,  1015   4TH  STREET, S.W.CALGARY, ALBERTA T2R 1J4TEL (403) 262-2799FAX (403) 262-2790

621  17TH STREET, SUITE 1550DENVER, COLORADO 80293-1501TEL (303) 623-9147FAX (303) 623-4258

EX-31.1

EXHIBIT 31.1

CERTIFICATIONS

I, Marvin F. Romanow, certify that:

1.   I have reviewed this annual report on Form 10-K/A of Nexen Inc.; and

2.   Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report.

Date: December 15, 2010

/s/ Marvin F. Romanow

Marvin F. Romanow

President and Chief Executive Officer

EX-31.2

EXHIBIT 31.2

CERTIFICATIONS

I, Kevin J. Reinhart, certify that:

1. I have reviewed this annual report on Form 10-K/A of Nexen Inc.; and

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report.

Date: December 15, 2010

/s/ Kevin J. Reinhart

Kevin J. Reinhart

Executive Vice President

and Chief Financial Officer