Nexen Announces Gulf of Mexico Joint Venture Partnership

CALGARY, ALBERTA--(Marketwire - Nov. 30, 2011) - Today, Nexen Inc. (TSX, NYSE: NXY) announced that we have concluded a joint venture with CNOOC Limited in the Gulf of Mexico. The joint venture will give CNOOC Limited a working interest in up to six deepwater exploration wells in the Gulf. Among the prospects included in the deal are the Kakuna well, which is currently drilling, and the Angel Fire well, which is expected to spud in 2012. CNOOC Limited will participate in Kakuna, Angel Fire, and Cypress with a 20% working interest. CNOOC Limited may also participate in three additional exploration wells with a 10% to 25% working interest. The venture does not include any interest in our Appomattox discovery or related Norphlet formation prospects.

"This agreement is the culmination of an extensive process to recognize some of the value our exploration team has created in the Gulf of Mexico," said Marvin Romanow, Nexen's President and CEO. "We are seeing a gradual return to normal activity in the Gulf and this deal is a reflection of the fact that the basin remains a very exciting one for deepwater exploration prospects."

"Nexen's strategy in the Gulf of Mexico is to mature prospects at a high working interest, and then utilize joint venture agreements like this one to reduce our interest to our target level of 25%-30%, while recognizing the potential of our exploration portfolio," continued Romanow.

Drilling on the Kakuna well on Green Canyon block 504 is currently in progress. We also expect to spud the Angel Fire well on Green Canyon block 327 in 2012.

Nexen currently produces approximately 20,000 barrels of oil equivalent per day in the Gulf of Mexico and is one of the top leaseholders in the deepwater Gulf. We also have a significant discovery at Appomattox, containing at least 250 million barrels of contingent recoverable resource, where we are currently drilling our first appraisal well. We have a 20% interest in Appomattox, the remainder is held by Shell, who is the operator.

Company Information

CNOOC Limited is China's largest producer of offshore crude oil and natural gas and one of the largest independent oil and gas exploration and production companies in the world. CNOOC Limited mainly engages in exploration, development, production and sales of oil and natural gas. CNOOC Limited has also become Nexen's partner on the Long Lake project in Alberta's Athabasca oil sands following the transaction to purchase OPTI Canada Inc.

Nexen Inc. is an independent, Canadian-based global energy company, listed on the Toronto and New York stock exchanges under the symbol NXY. Nexen is focused on three growth strategies: oil sands and shale gas in Western Canada and conventional exploration and development primarily in the North Sea, offshore West Africa and deepwater Gulf of Mexico. Nexen adds value for shareholders through successful full-cycle oil and gas exploration and development, and leadership in ethics, integrity, governance and environmental stewardship.

For further information on Appomattox resource disclosure, please refer to our press release dated September 27th, 2010.

Forward-Looking Statements

Certain statements in this release constitute "forward-looking statements" (within the meaning of the United States Private Securities Litigation Reform Act of 1995, as amended) or "forward-looking information" (within the meaning of applicable Canadian securities legislation). Such statements or information (together "forward-looking statements") are generally identifiable by the forward-looking terminology used such as "anticipate", "believe", "intend", "plan", "expect", "estimate", "budget", "outlook", "forecast" or other similar words and include statements relating to or associated with individual wells, regions or projects. Any statements as to possible future crude oil, natural gas or chemicals prices; future production levels; future royalties and tax levels; future capital expenditures, their timing and their allocation to exploration and development activities; future earnings; future asset acquisitions or dispositions; future sources of funding for our capital program; future debt levels; availability of committed credit facilities; possible commerciality of our projects; development plans or capacity expansions; the expectation that we have the ability to substantially grow production at our oil sands facilities through controlled expansions; the expectation of achieving the production design rates from our oil sands facilities; the expectation that our oil sands production facilities continue to develop better and more sustainable practices;

the expectation of cheaper and more technologically advanced operations; the expected design size of our operations; the expected timing and associated production impact of facilities turnarounds and maintenance; the expectation that we can continue to operate our offshore exploration, development and production facilities safely and profitably; future ability to execute dispositions of assets or businesses; future sources of liquidity, cash flows and their uses; future drilling of new wells; ultimate recoverability of current and long-term assets; ultimate recoverability of reserves or resources; expected finding and development costs; expected operating costs, future cost recovery oil revenues from our Yemen operations; the expectation of negotiating of an extension to certain of our production sharing agreements; the expectation of our ability to comply with the new safety and environmental rules enacted in the US at a minimal incremental cost, and of receiving necessary drilling permits for our US offshore operations; future demand for chemicals products; estimates on a per share basis; future foreign currency exchange rates, future expenditures and future allowances relating to environmental matters and our ability to comply therewith; dates by which certain areas will be developed, come on stream or reach expected operating capacity; and changes in any of the foregoing are forward-looking statements. Statements relating to "reserves" or "resources" are forward-looking statements, as they involve the implied assessment, based on estimates and assumptions that the reserves and resources described exist in the quantities predicted or estimated, and can be profitably produced in the future.

All of the forward-looking statements in this release are qualified by the assumptions that are stated or inherent in such forward-looking statements. Although we believe that these assumptions are reasonable, this list is not exhaustive of the factors that may affect any of the forward-looking statements and the reader should not place an undue reliance on these assumptions and such forward-looking statements. The key assumptions that have been made in connection with the forward-looking statements include the following: that we will conduct our operations and achieve results of operations as anticipated; that our development plans will achieve the expected results; the general continuance of current or, where applicable, assumed industry conditions; the continuation of assumed tax, royalty and regulatory regimes; the accuracy of the estimates of our reserve volumes; commodity price and cost assumptions; the continued availability of adequate cash flow and debt and/or equity financing to fund our capital and operating requirements as needed; and the extent of our liabilities. We believe the material factors, expectations and assumptions reflected in the forward-looking statements are reasonable, but no assurance can be given that these factors, expectations and assumptions will prove to be correct.

The forward-looking statements are subject to known and unknown risks and uncertainties and other factors which may cause actual results, levels of activity and achievements to differ materially from those expressed or implied by such statements. Such factors include, among others: market prices for oil and gas; our ability to explore, develop, produce, upgrade and transport crude oil and natural gas to markets; ultimate effectiveness of design or design modifications to facilities; the results of exploration and development drilling and related activities; the cumulative impact of oil sands development on the environment; the impact of technology on operations and processes and how new complex technology may not perform as expected; the availability of pipeline and global refining capacity; risks inherent to the operations of any large, complex refinery units, especially the integration between production operations and an upgrader facility; availability of third-party bitumen for use in our oil sands production facilities; labour and material shortages; risks related to accidents, blowouts and spills in connection with our offshore exploration, development and production activities, particularly our deepwater activities; direct and indirect risks related to the imposition of moratoriums, suspensions or cancellations of our offshore exploration, development and production operations, particularly our deepwater activities; the impact of severe weather on our offshore exploration, development and production activities, particularly our deepwater activities; the effectiveness and reliability of our technology in harsh and unpredictable environments; risks related to the actions and financial circumstances of our agents, counterparties, contractors, and joint venture parties; volatility in energy trading markets; foreign currency exchange rates; economic conditions in the countries and regions in which we carry on business; governmental actions including changes to taxes or royalties, changes in environmental and other laws and regulations including without limitation, those related to our offshore exploration, development and production activities; renegotiations of contracts; results of litigation, arbitration or regulatory proceedings; political uncertainty, including actions by terrorists, insurgent or other groups, or other armed conflict, including conflict between states; and other factors, many of which are beyond our control.

The impact of any one risk, uncertainty or factor on a particular forward-looking statement is not determinable with certainty as these factors are interdependent, and management's future course of action would depend on our assessment of all information at that time. Although we believe that the expectations conveyed by the forward-looking statements are reasonable based on information available to us on the date such forward-looking statements were made, no assurances can be given as to future results, levels of activity and achievements. Undue reliance should not be placed on the forward-looking statements contained herein, which are made as of the date hereof and, except as required by law, Nexen undertakes no obligation to update publicly or revise any forward-looking statements, whether as a result of new information, future events or otherwise. The forward-looking statements contained herein are expressly qualified by this cautionary statement. Readers should also refer to the Risk Factors contained in our 2010 Annual Information form, and to the Quantitative Disclosures about Market Risk and our Forward Looking Statements contained in our 2010 Management Discussion and Analysis.

Cautionary Note to US Investors

In this disclosure, we may refer to "recoverable reserves", "recoverable resources", "recoverable contingent resources" and "prospective resources" which are inherently more uncertain than proved reserves or probable reserves. These terms are not used in our filings with the SEC. Our reserves and related performance measures represent our working interest before royalties, unless otherwise indicated. Please refer to our Annual Information Form available under our profile on SEDAR at www.sedar.com for further reserves disclosure.

Cautionary Note to Canadian Investors

Nexen has received an exemption from the securities regulatory authorities in the various provinces of Canada from certain requirements of National Instrument 51-101 Standards of Disclosure for Oil and Gas Activities ("NI 51-101") that permits us to disclose reserves estimates and related disclosures that have been prepared in accordance with SEC requirements.

As a result of this exemption, Nexen's disclosures may differ from other Canadian companies and investors should note the following fundamental differences between reserves estimates and related disclosures prepared in accordance with SEC requirements and those prepared in accordance with NI 51-101:

--  SEC reserves estimates are based upon different reserves definitions and
    are prepared in accordance with generally recognized industry practices
    in the US whereas NI 51-101 reserves are based on definitions and
    standards promulgated by the Canadian Oil and Gas Evaluation Handbook
    ("COGE Handbook") and generally recognized industry practices in Canada;
--  SEC reserves definitions differ from NI 51-101 in areas such as the use
    of reliable technology, areal extent around a drilled location,
    quantities below the lowest known oil and quantities across an undrilled
    fault block; 
--  the SEC mandates disclosure of proved reserves and the Standardized
    Measure of Discounted Future Net Cash Flows and Changes Therein
    calculated using the year's monthly average prices and costs held
    constant whereas NI 51-101 requires disclosure of reserves and related
    future net revenues using forecast prices and costs; 
--  the SEC mandates disclosure of reserves by geographic area whereas NI
    51-101 requires disclosure of reserves by additional categories and
    product types; 
--  the SEC does not require the disclosure of future net revenue of proved
    and proved plus probable reserves using forecast pricing at various
    discount rates; 
--  the SEC requires future development costs to be estimated using existing
    conditions held constant, whereas NI 51-101 requires estimation using
    forecast conditions; 
--  the SEC does not require the validation of reserves estimates by
    independent qualified reserves evaluators or auditors, whereas, without
    an exemption noted below, NI 51-101 requires issuers to engage such
    evaluators or auditors to evaluate, audit or review reserves and related
    future net revenue attributable to those reserves; and 
--  the SEC does not allow proved and probable reserves to be aggregated
    whereas NI 51-101 requires issuers to make such aggregation.

The foregoing is a general description of the principal differences only.   
The differences between SEC requirements and NI 51-101 may be material for  
certain properties. Please also note:                                       

--  we use oil equivalents (boe) to express quantities of natural gas and
    crude oil in a common unit. A conversion ratio of 6 mcf of natural gas
    to 1 barrel of oil is used. Boe may be misleading, particularly if used
    in isolation. The conversion ratio is based on an energy equivalency
    conversion method primarily applicable at the burner tip and does not
    represent a value equivalency at the wellhead; and 
--  because reserves data are based on judgments regarding future events
    actual results will vary and the variations may be material. Variations
    as a result of future events are expected to be consistent with the fact
    that reserves are categorized according to the probability of their
    recovery. 

Nexen has also received an exemption from NI 51-101 that permits us to forego the requirement to have our reserves and related future net revenue attributable to our reserves evaluated, audited or reviewed by an independent qualified reserves evaluator or auditor. Accordingly, our future net revenue and reserves estimates are based on internal evaluations. Due to the extent and expertise of our internal reserves evaluation resources, our staff's familiarity with our properties and the controls applied to the evaluation process, we believe the reliability of our internally generated reserves estimates is not materially less than would be generated by an independent reserves evaluator.

Resources

The resource estimates contained in this news release were announced on September 27, 2010 and were prepared by qualified reserves evaluators. The estimated contingent and prospective resources in this news release reflects all of our low, high and best case of recoverable resources. A "best estimate" is the best estimate of the quantity of resources that will actually be recovered. It is equally likely that the actual quantities recovered will be greater or less than the best estimate. Those resources that fall within the best estimate have a 50% confidence level that the actual quantities recovered will equal or exceed the estimate. The 'low estimate' and 'high estimate' are considered to be conservative and optimistic estimates of resources with 90% and 10% confidence respectively. Nexen's estimates of contingent and prospective resources are based on definitions set out in the Canadian Oil and Gas Evaluation Handbook. Contingent resources are quantities of petroleum estimated, as of a given date, to be potentially recoverable from known accumulations using established technology or technology under development, but which are not currently considered to be commercially recoverable due to one or more contingencies. Prospective resources are quantities of petroleum estimated, as of a given date, to be potentially recoverable from undiscovered accumulations by application of future development projects.

Contingencies on resources may include, but are not limited to, factors such as economic, legal, environmental, political and regulatory matters or a lack of markets. Specific oil sands contingencies precluding these contingent resources being classified as reserves include but are not limited to: project sanction, the cost and effectiveness of steam-assisted gravity drainage application, stakeholder and regulatory approvals, access to required services and infrastructure, oil prices and a demonstration of economic viability. There is no certainty that it will be commercially viable to produce any portion of these contingent oil sands resources.

Cautionary statement: In the case of discovered resources or a subcategory of discovered resources other than reserves, there is no certainty that it will be commercially viable to produce any portion of the resources. In the case of undiscovered resources or a subcategory of undiscovered resources, there is no certainty that any portion of the resources will be discovered. If discovered, there is no certainty that it will be commercially viable to produce any portion of the resources.