================================================================================ UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 11-K (Mark One) [X] ANNUAL REPORT PURSUANT TO SECTION 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 FOR THE FISCAL YEAR ENDED DECEMBER 31, 2005 OR [_] TRANSITION REPORT PURSUANT TO SECTION 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 FOR THE TRANSITION PERIOD FROM __________ TO __________ COMMISSION FILE NO. 001-06702 A. Full title of the plan and address of the plan, if different from that of the issuer named below: NEXEN SAVINGS PLAN 12790 Merit Drive, Suite 800 Dallas, Texas 75251-1270 B. Name of issuer of the securities held pursuant to the plan and the address of its principal executive office: NEXEN INC. 801 - 7th Avenue SW Calgary, Alberta, Canada T2P 3P7 ================================================================================ NEXEN SAVINGS PLAN FINANCIAL STATEMENTS AND SUPPLEMENTAL SCHEDULE - ------------------------------------------------------------------------------- DECEMBER 31, 2005 TABLE OF CONTENTS REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM 1 FINANCIAL STATEMENTS Statements of Net Assets Available for Benefits 2 Statements of Changes in Net Assets Available for Benefits 3 Notes to Financial Statements 4 SUPPLEMENTAL SCHEDULE * Schedule H, line 4i - Schedule of Assets (Held at End of Year) 9 * Other schedules required by 29 CFR 2520.103-10 of the Department of Labor's Rules and Regulations for Reporting and Disclosure under Employee Retirement Income Security Act of 1974 have been omitted because they are not applicable. REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM To the Administrative Committee NEXEN SAVINGS PLAN Dallas, Texas We have audited the accompanying statements of net assets available for benefits of the Nexen Savings Plan (the "Plan") as of December 31, 2005 and 2004, and the related statements of changes in net assets available for benefits for the years then ended. These financial statements and the supplemental schedule referred to below are the responsibility of the Plan's Administrative Committee. Our responsibility is to express an opinion on these financial statements and schedule based on our audits. We conducted our audits in accordance with the standards of the Public Company Accounting Oversight Board (United States). Those standards require that we plan and perform the audits to obtain reasonable assurance about whether the financial statements are free of material misstatement. An audit includes examining, on a test basis, evidence supporting the amounts and disclosures in the financial statements. An audit also includes assessing the accounting principles used and significant estimates made by management, as well as evaluating the overall financial statement presentation. We believe that our audits provide a reasonable basis for our opinion. In our opinion, the financial statements referred to above present fairly, in all material respects, the net assets available for benefits of the Nexen Savings Plan as of December 31, 2005 and 2004, and the changes in its net assets available for benefits for the years then ended, in conformity with accounting principles generally accepted in the United States of America. Our audits were performed for the purpose of forming an opinion on the basic financial statements taken as a whole. The supplemental schedule of assets (held at end of year) is presented for purposes of additional analysis and is not a required part of the basic financial statements but is supplementary information required by the Department of Labor's Rules and Regulations for Reporting and Disclosure under the Employee Retirement Income Security Act of 1974. The supplemental schedule has been subjected to the auditing procedures applied in the audit of the basic financial statements and, in our opinion, is fairly stated in all material respects in relation to the basic financial statements taken as a whole. WEAVER AND TIDWELL, L.L.P. Dallas, Texas June 8, 2006 NEXEN SAVINGS PLAN STATEMENTS OF NET ASSETS AVAILABLE FOR BENEFITS DECEMBER 31, 2005 AND 2004 2005 2004 ----------- ----------- ASSETS Cash $ 352 $ 2,927 Investments, at fair value 45,552,975 32,693,915 Receivables for securities sold 181,533 Participant contributions receivable 1,439 Accrued dividends receivable 13,558 12,210 Participant loans 969,883 941,365 ----------- ----------- TOTAL ASSETS 46,538,207 33,831,950 ----------- ----------- LIABILITIES Payables for securities purchased 184,015 Other payables 5 224 ----------- ----------- TOTAL LIABILITIES 5 184,239 ----------- ----------- NET ASSETS AVAILABLE FOR BENEFITS $46,538,202 $33,647,711 =========== =========== The Notes to Financial Statements are an integral part of these statements 2 NEXEN SAVINGS PLAN STATEMENTS OF CHANGES IN NET ASSETS AVAILABLE FOR BENEFITS YEARS ENDED DECEMBER 31, 2005 AND 2004 2005 2004 ----------- ----------- ADDITIONS Investment income: Net appreciation in fair value of investments $ 9,946,256 $ 2,982,992 Interest 271,859 231,387 Dividends 1,369,008 572,298 ----------- ----------- 11,587,123 3,786,677 ----------- ----------- Contributions: Participants 1,980,100 1,752,603 Employer 1,193,594 1,108,541 Rollover 47,204 296,621 ----------- ----------- 3,220,898 3,157,765 ----------- ----------- TOTAL ADDITIONS 14,808,021 6,944,442 ----------- ----------- DEDUCTIONS Benefits paid to participants 1,912,767 971,453 Administrative expenses 4,763 5,337 ----------- ----------- TOTAL DEDUCTIONS 1,917,530 976,790 ----------- ----------- NET INCREASE IN NET ASSETS AVAILABLE 12,890,491 5,967,652 NET ASSETS AVAILABLE FOR BENEFITS Beginning of year 33,647,711 27,680,059 ----------- ----------- NET ASSETS AVAILABLE FOR BENEFITS End of year $46,538,202 $33,647,711 =========== =========== The Notes to Financial Statements are an integral part of these statements 3 NEXEN SAVINGS PLAN NOTES TO FINANCIAL STATEMENTS Note 1. Description of the Plan The following description of the Nexen Savings Plan (the "Plan") is provided for general information purposes only. More complete information regarding the Plan's provisions may be found in the Plan Document. The Plan is a defined contribution plan that was adopted September 1, 1988, and amended and restated effective January 1, 2002, to provide eligible employees of Nexen Petroleum U.S.A. Inc. (the "Company") and participating employers, Nexen Chemicals U.S.A. Inc., Nexen Marketing U.S.A. Inc., Nexen Oil and Gas U.S.A. Inc., and Nexen Petroleum International (U.S.A.) Inc. (the "Participating Employers"), wholly owned subsidiaries of Nexen Inc., and Canexus U.S. Inc., a method to meet their long-range financial objectives under the requirements of Section 401(k) of the Internal Revenue Code. For the years ended December 31, 2005 and 2004, Nationwide Trust Company, FSB (the "Trustee") was the Plan Trustee with the recordkeeping function performed by The 401(k) Company (the "Recordkeeper"). All regular employees of the Company and Participating Employers who are 18 years of age and over are eligible to participate in the Plan on the entry date coinciding with or next following the date the employee attains age 18. Participant contributions are made on a voluntary basis and directly withheld from the participant's eligible compensation, as defined in the Plan Document. Contributions may be made with pretax dollars, after-tax dollars, or a combination of pretax and after-tax dollars. Eligible compensation excludes overtime and bonuses. Participants are immediately vested in their employee contribution account and actual earnings thereon. The Company and Participating Employers will match 100 percent of Participant contributions up to 6% of the Participant's eligible compensation. In addition, a Participant who completes one hour of service after January 1, 2000, shall be vested 100% in his or her employer matching account. The Plan's investment options are: (1) Stable Value Trust Fund, (2) Bond Fund of America A, (3) Delaware Group: REIT Fund A, (4) Managers Special Equity Fund, (5) Scudder Equity 500 Index Fund, (6) Growth Fund of America A, (7) First Eagle Overseas Fund A, (8) EuroPacific Growth Fund A, (9) Washington Mutual Investors Fund A, (10) Oppenheimer Developing Markets Fund A, (11) Third Avenue Value Fund, (12) American Beacon Small Cap Value Plan, and (13) Nexen Inc. Stock Fund. All Company and Participating Employers contributions are invested in accordance with the investment choices selected by each respective Participant. Distribution of a Participant's entire account becomes due in three ways: (1) upon termination of employment, (2) death, or (3) disability, as defined in the Plan Document. At the option of the Participant or beneficiary, such account balances may be distributed in a lump-sum payment or via periodic installment payments as described in the Plan Document. Withdrawals from the Plan by active Participants are permitted for specific instances of financial hardship and age 59 1/2 withdrawals, which can be made once every six months. Once per Plan year, a Participant may withdraw a portion or all of his or her after-tax and rollover account, subject to a $250 minimum. In December 2005, the Financial Accounting Standards Board issued Statement of Position (SOP) 94-4-1, "REPORTING OF FULLY BENEFIT-RESPONSIVE INVESTMENT CONTRACTS HELD BY CERTAIN INVESTMENT COMPANIES SUBJECT TO THE AICPA INVESTMENT COMPANY GUIDE AND DEFINED-CONTRIBUTION HEALTH AND WELFARE AND PENSION PLANS," which affects defined contribution pension plans and health and welfare plans that hold fully benefit-responsive investment contracts. Presently, the Plan has no investment contracts that are considered fully benefit-responsive for purposes of SOP 94-4-1 4 NEXEN SAVINGS PLAN NOTES TO FINANCIAL STATEMENTS Note 2. Summary of Significant Accounting Policies Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the reported amounts of net assets available for benefits and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of additions to and deductions from net assets available for benefits during the reporting period. Actual results could differ from those estimates. Basis of Accounting The financial statements of the Plan are presented on the accrual basis of accounting in accordance with accounting principles generally accepted in the United States of America. Current year contributions, expenses, and investment income, including both interest and dividends, which are not received or paid until the subsequent year, are accrued in the current year. Benefits are recorded when paid. Investments Investments are stated at fair value as determined by the Trust based on quoted market prices at the Plan's year end. Purchases and sales of investments are recorded on a trade date basis. Participants may direct their contributions and any related earnings into thirteen distinct investment options, including the Nexen Inc. Stock Fund. Interest is allocated to Participant accounts on a pro-rata basis depending on the Participants' account balance. Dividends are allocated based on the number of shares in a Participant's account. A brief description of each investment option is as follows: STABLE VALUE TRUST FUND - The Stable Value Trust Fund's core investment vehicle is the AMVESCAP National Trust Company Stable Value Trust Fund. The remaining portion of the money is invested in money market funds offered through the following mutual fund families: The American Funds Group, Oppenheimer Funds, Managers Funds, Third Avenue Funds, Delaware Funds, First Eagle Funds, and Scudder Funds. AMERICAN BEACON SMALL CAP VALUE PLAN - is a small value fund that seeks long-term capital appreciation and current income by investing over 80% of its assets in equity securities of companies within the United States. BOND FUND OF AMERICA A - invests primarily in high quality intermediate-term corporate bonds and U.S. government securities. DELAWARE GROUP: REIT FUND A - is a non-diversified fund that seeks long-term total return by investing primarily in equities of real-estate investment trusts (REITs). MANAGERS SPECIAL EQUITY FUND - is a small growth fund that seeks long-term capital appreciation by investing at least 80% of assets in equity securities. SCUDDER EQUITY 500 INDEX FUND - is a large company growth and income fund that invests primarily in equity securities of companies included in the S & P 500. 5 NEXEN SAVINGS PLAN NOTES TO FINANCIAL STATEMENTS Note 2. Summary of Significant Accounting Policies - continued Investments - continued GROWTH FUND OF AMERICA A - is a large growth fund that seeks capital growth by investing primarily in common stocks. The fund may invest up to 15% of assets in securities of issuers domiciled outside of the United States and Canada. FIRST EAGLE OVERSEAS FUND A - is a foreign stock fund that seeks long-term capital growth by investing primarily in equities of small- and mid-sized foreign companies in developed and emerging markets. EUROPACIFIC GROWTH FUND A - is a large company foreign stock fund that seeks long-term capital appreciation by investing in companies domiciled in developed countries outside the United States. WASHINGTON MUTUAL INVESTORS FUND A - is a large company value-oriented growth and income fund. OPPENHEIMER DEVELOPING MARKETS FUND A - is an emerging markets stock fund that seeks long-term growth by investing in stock of issues in countries with developing markets. THIRD AVENUE VALUE FUND - is a small value fund that seeks long-term capital appreciation by investing in equity securities issued by companies that are believed to be undervalued and to have strong financial positions and responsible management. NEXEN INC. STOCK FUND - provides ownership interest in Nexen Inc. Common Stock with short-term cash sufficient to maintain a liquidity balance to facilitate daily transactions and compliance with securities law. Market and Credit Risks The Plan invests in a variety of investments. Investments are exposed to various risks, such as interest rate, market and credit risks. Due to the level of risk associated with certain investments, it is at least reasonably possible that the changes in the values of the investments will occur in the near term and that such changes could materially affect the amount reported in the Plan's statement of net assets available for benefits. Administration The Plan is administered by the Administrative Committee, which is composed of members who are either officers or employees of the Company. Investment options for the Plan are selected by the Benefit Plan Design Committee from funds available through the Recordkeeper. Some of the fund providers charge 12b-1 fees at the fund level before earnings are paid to investors. The Recordkeeper receives fees from these fund providers from 12b-1 fees charged to the funds. 12b-1 fees received by the Recordkeeper are based on Plan assets invested in each fund. Similarly, all Trustee fees for the Plan are received from 12b-1 fees charged to the funds. 12b-1 fees received by the Trustee are also based on Plan assets invested in each fund. 6 NEXEN SAVINGS PLAN NOTES TO FINANCIAL STATEMENTS Note 2. Summary of Significant Accounting Policies - continued Loans to Participants Participant loans receivable are stated at cost, which approximates fair value. A Participant may borrow up to the lesser of 50% of his or her vested account balance or $50,000 with a minimum loan amount of $1,000. Loans are repayable through payroll deductions over periods ranging up to 60 months. Participants are charged a $50 loan set-up fee with a $2 monthly maintenance fee per loan. The loans are secured by a lien on the borrower's vested account balance in the Plan and bear interest at rates based on prevailing market conditions. Interest rates on outstanding loans at December 31, 2005 ranged from 5.76% to 9.25%. Plan Termination Although it has not expressed any intention to do so, the Company has the right to terminate the Plan pursuant to provisions set forth by the Plan Document and subject to the provisions of ERISA. In the event of Plan termination, each Participant's account shall become fully vested and Participants will be entitled to distributions of their entire accounts. Note 3. Tax Status The Plan received a favorable determination letter from the Internal Revenue Service dated April 5, 2002, stating that the Plan and its amendments are qualified under Section 401(a) of the Internal Revenue Code of 1986, as amended (the "Code"), and the Trust is exempt from taxation under Section 501(a) of the Code. The Trust established under the Plan to hold the Plan's assets is intended to qualify pursuant to the appropriate section of the Internal Revenue Code as a tax-exempt organization. The plan has been amended since receiving the determination letter. However, the Company and the Plan's tax counsel believe that the Trust continues to qualify and to operate as designed. Note 4. Investments Investments that represent 5% or more of the net assets available for Plan benefits at December 31, 2005 and 2004 are as follows: December 31, December 31, 2005 2004 Fair Value Fair Value ------------ ------------ Bond Fund of America A $ 3,150,948 $ 2,459,382 EuroPacrfic Growth Fund A 2,755,028 2,213,910 Nexen Inc. Stock Fund 15,072,085 6,934,421 Stable Value Fund 5,501,169 5,097,765 Third Avenue Value Fund 2,518,717 1,993,099 Washington Mutual Investors Fund A 4,399,742 4,092,367 Growth Fund of America A 2,608,119 Delaware Group REIT Fund A 1,722,598 MFS Massachusetss Investors Growth Fund A 2,097,425 7 NEXEN SAVINGS PLAN NOTES TO FINANCIAL STATEMENTS Note 4. Investments - continued During 2005 and 2004, the Plan's investments (including gains and losses on investments bought and sold, as well as held during the year) increased in value by $11,587,123 and $3,786,677, respectively, as follows: 2005 2004 ---------------------------- -------------------------- Realized and Realized and Interest and Unrealized Interest and Unrealized Dividends Gains Dividends Gains ------------ ------------- ------------ ------------ Mutual funds $ 1,519,930 $ 1,015,736 $ 688,502 $ 2,002,637 Stock funds 53,924 8,930,520 55,876 980,355 Loans to Participants 67,013 59,307 Note 5. Plan Amendments On March 8, 2005, the Fifth Amendment to the Nexen Savings Plan was executed and adopted effective March 28, 2005. The purpose of this amendment was to change the Plan's cash-out distribution dollar limit from $5,000 to $1,000. On August 17, 2005, the Sixth Amendment to the Nexen Savings Plan was executed and adopted. Effective August 18, 2005, Section XIII of the Adoption Agreement was amended to add Canexus U.S. Inc. as a Participating Employer covered under the Plan. 8 SUPPLEMENTAL SCHEDULE NEXEN SAVINGS PLAN Schedule H, Line 4i - SCHEDULE OF ASSETS (HELD AT END OF YEAR) EIN: 06-0944810 PLAN NUMBER 001 December 31, 2005 (a) (b) (c) (d) (e) Description of Investment including Identity of Issuer, borrower maturity date, rate of investment, Current lessor, or similar party collateral, par, or maturity value Cost # value - -------- ------------------------------- ------------------------------------------- --------- ------------ PARTICIPANT-DIRECTED INVESTMENTS: The American Funds Group Bond Fund of America A, Net Asset Value $13.22 $ 3,150,948 The American Funds Group Washington Mutual Investors Fund A, Net Asset Value $30.84 4,399,742 The American Funds Group EuroPacific Growth Fund A, Net Asset Value $41.10 2,755,028 American Beacon American Beacon Small Cap Value Plan Net Asset Value $20.03 845,029 Scudder Funds Scudder Equity 500 Index Fund, Net Asset Value $139.85 1,884,097 First Eagle Funds First Eagle Overseas Fund A, Net Asset Value $23.04 1,323,872 Managers Funds Managers Special Equity Fund Net Asset Value $86.77 1,597,513 The American Funds Group Growth Fund of America A, Net Asset Value $30.86 2,608,119 Third Avenue Funds Third Avenue Value Fund, Net Asset Value $54.78 2,518,717 Delaware Funds Delaware Group: REIT Fund A, Net Asset Value $19.18 2,121,991 Oppenheimer Funds Oppenheimer Developing Markets Fund A, Net Asset Value $36.33 1,364,984 The American Funds Group Cash Management Trust Of America, Par Value $1.00 409,681 AMVESCAP National Trust Company Stable Value Trust Fund, Par Value $1.00 5,501,169 AllianceBernstein Capital Reserve Money Market Fund Par Value $1.00 115 Chase Bank, NA Cash 237 * Nexen Inc. Nexen Inc. Stock Fund (Nexen Inc. Stock, no par, Net Asset Value $47.63) 15,072,085 * Loans to Participants Interest Rates From 5.76% to 9.25% 969,883 ------------ $ 46,523,210 ============ * Indicates each identified person/entity known to be party-in-interest. # Historical cost information omitted as it is not required for participant-directed investments. This supplemental schedule lists assets held for investment purposes at December 31, 2005, as required by the Department of Labor's Rules and Regulations for Reporting and Disclosure. 9 SIGNATURES THE PLAN. Pursuant to the requirements of the Securities Exchange Act of 1934, Nexen Petroleum U.S.A. Inc. has duly caused this annual report to be signed on its behalf by the undersigned hereunto duly authorized. DATED: June 28, 2006 NEXEN SAVINGS PLAN By: Nexen Petroleum U.S.A. Inc. By: /s/ Douglas B. Otten ---------------------------- Douglas B. Otten, President INDEX TO EXHIBITS EXHIBIT NUMBER DESCRIPTION OF EXHIBITS ------- ----------------------- 1 Consent of Weaver & Tidwell, L.L.P.