Exhibit 99

ANADARKO ANNOUNCES FIRST-QUARTER RESULTS

HOUSTON, May 2, 2011 – Anadarko Petroleum Corporation (NYSE: APC) today announced first-quarter 2011 net income attributable to common stockholders of $216 million, or $0.43 per share (diluted). These results include certain items typically excluded by the investment community in published estimates. In total, these items decreased net income by approximately $147 million, or $0.29 per share (diluted) on an after-tax basis.⁽¹⁾ Cash flow from operating activities in the first quarter of 2011 was $1.289 billion, and discretionary cash flow totaled $1.674 billion.⁽²⁾

FIRST-QUARTER 2011 HIGHLIGHTS

“Anadarko delivered record sales volumes in the first quarter, including a 15-percent quarter-over-quarter increase in daily liquids volumes, strong cash flow and improved margins,” said Anadarko Chairman and CEO Jim Hackett. “This record performance was highlighted by the rapid growth of our shale plays and our first lifting from the Jubilee field offshore Ghana. Our deepwater exploration program also achieved excellent results in the quarter with three discoveries and three successful offshore appraisal wells. Early in the second quarter, we closed the previously announced $1.6 billion joint venture with KNOC (Korea National Oil Corporation) in the Eagleford Shale, validating the tremendous embedded value of this resource.”

During the first quarter of 2011, sales volumes totaled 62 million barrels of oil equivalent (BOE), or 690,000 BOE per day, averaging approximately 2.4 billion cubic feet of

natural gas per day, 212,000 barrels of oil per day (BOPD), and 76,000 barrels of natural gas liquids per day.

OPERATIONS SUMMARY

Anadarko’s record sales volumes benefited from the company’s first oil lifting at the Jubilee field in Ghana, as well as continued production growth in the Eagleford and Marcellus shale plays. In Ghana, current gross production from the Jubilee field is more than 70,000 BOPD and continues to ramp up toward capacity of 120,000 BOPD, which is expected by the third quarter of 2011. In the company’s shale plays, average sales volumes in the Eagleford and Marcellus areas increased by about 30 percent and 82 percent, respectively, over the fourth quarter of 2010.

The company recently closed the $1.6 billion Eagleford joint-venture agreement with a subsidiary of KNOC. Under the terms of the agreement, KNOC will fund approximately 100 percent of capital costs in the play for the remainder of this year and up to 90 percent of costs thereafter, until the carry is exhausted. The amount to be paid includes an approximate $48 million post-effective date reimbursement, and KNOC also exercised its option to acquire an approximate 25-percent interest in associated midstream assets for reimbursement of an additional $38 million.

In the Rockies, Anadarko announced the acquisition of the Wattenberg Processing Plant in northeastern Colorado. This acquisition is expected to improve field recoveries and allow for future expansion in the greater Denver-Julesburg Basin, where Anadarko continues an active program with seven rigs drilling directional wells in the Wattenberg field and three rigs drilling horizontal wells in the emerging Niobrara play.

EXPLORATION SUMMARY

Anadarko announced three deepwater discoveries during the first quarter of 2011. The Teak-1 and Teak-2 discoveries, located in the 30.875-percent-owned West Cape Three Points Block offshore Ghana, encountered high-quality oil, condensate and natural gas pay in Turonian-age reservoirs similar to those found in the adjacent Jubilee field, as well as Campanian-age reservoirs. In Mozambique, the company announced the Tubarão discovery, marking its

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fourth operated natural gas discovery in the 36.5 percent-owned Offshore Area 1 of the Rovuma Basin.

In the Deepwater Tano Block offshore Ghana, where Anadarko holds an 18-percent working interest, the company and its partners announced successful appraisal wells at Enyenra-2A, Tweneboa-3 and Tweneboa-3ST. Subsequent to quarter end, the operator also announced the successful Tweneboa-4 appraisal well. Additional appraisal activity is ongoing in the Tweneboa/Enyenra complex as the partnership continues to work toward a declaration of commerciality, which is expected later this year.

FINANCIAL SUMMARY

Anadarko ended the first quarter of 2011 with approximately $3.5 billion of cash on hand, maintained access to its five-year, $5 billion undrawn credit facility and generated $87 million of free cash flow. The company’s estimated 2011 capital expenditures were increased by approximately $600 million as a result of the Wattenberg Processing Plant acquisition, resulting in an estimated capital spending range of $6.2 to $6.6 billion, excluding capital expenditures related to Western Gas Partners, LP.

OPERATIONS REPORT

For more details on Anadarko’s operations, please refer to the comprehensive report on first-quarter 2011 activity. The report is available at www.anadarko.com on the Investor Relations page.

CONFERENCE CALL TOMORROW AT 9 A.M. CDT, 10 A.M. EDT

Anadarko will host a conference call on Tuesday, May 3, at 9 a.m. Central Daylight Time (10 a.m. Eastern Daylight Time) to discuss first-quarter results, current operations and the company’s outlook for the remainder of 2011. The dial-in number is 888.713.4217 in the United States or 617.213.4869 internationally. The confirmation number is 98218183. For complete instructions on how to participate in the conference call, or to listen to the live audio webcast and slide presentation, please visit www.anadarko.com. A replay of the call will also be available on the Web site for approximately 30 days following the conference call.

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FINANCIAL DATA

Eight pages of summary financial data follow, including current hedge positions, financial guidance and supplemental production guidance.

⁽¹⁾ See the accompanying table for details of certain items affecting comparability.

⁽²⁾ See the accompanying table for a reconciliation of GAAP to non-GAAP financial measures and a statement indicating why management believes the non-GAAP financial measures provide useful information for investors.

Anadarko Petroleum Corporation’s mission is to deliver a competitive and sustainable rate of return to shareholders by exploring for, acquiring and developing oil and natural gas resources vital to the world’s health and welfare. As of year-end 2010, the company had approximately 2.42 billion barrels-equivalent of proved reserves, making it one of the world’s largest independent exploration and production companies. For more information about Anadarko, please visit www.anadarko.com.

This news release contains forward-looking statements within the meaning of Section 27A of the Securities Act of 1933 and Section 21E of the Securities Exchange Act of 1934. Anadarko believes that its expectations are based on reasonable assumptions. No assurance, however, can be given that such expectations will prove to have been correct. A number of factors could cause actual results to differ materially from the projections, anticipated results or other expectations expressed in this news release, including Anadarko’s ability to commercially operate the drilling prospects identified in this news release. See “Risk Factors” in the company’s 2010 Annual Report on Form 10-K, Quarterly Reports on Form 10-Q and other public filings and press releases. Anadarko undertakes no obligation to publicly update or revise any forward-looking statements.

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ANADARKO CONTACTS

MEDIA:

John Christiansen, john.christiansen@anadarko.com, 832.636.8736

Brian Cain, brian.cain@anadarko.com, 832.636.3404

INVESTORS:

John Colglazier, john.colglazier@anadarko.com, 832.636.2306

Dean Hennings, dean.hennings@anadarko.com, 832.636.2462

Wayne Rodrigs, wayne.rodrigs@anadarko.com, 832.636.2305

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Anadarko Petroleum Corporation

Certain Items Affecting Comparability

Reconciliation of GAAP to Non-GAAP Measures

Below are reconciliations of cash provided by operating activities (GAAP) to discretionary cash flow from operations and free cash flow (non-GAAP), and net income (loss) attributable to common stockholders (GAAP) to adjusted net income (loss) (non-GAAP) as required under Regulation G of the Securities Exchange Act of 1934. Management uses discretionary cash flow from operations and free cash flow to demonstrate the Company’s ability to internally fund capital expenditures and to service or incur additional debt. It is useful in comparisons of oil and gas exploration and production companies because it excludes fluctuations in assets and liabilities. Management uses adjusted net income (loss) to evaluate the Company’s operational trends and performance.

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Anadarko Petroleum Corporation

Reconciliation of GAAP to Non-GAAP Measures

Presented below is a reconciliation of total debt (GAAP) to net debt (non-GAAP). Management uses net debt as a measure of the Company’s outstanding debt obligations that would not be readily satisfied by its cash and cash equivalents on hand.

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Anadarko Petroleum Corporation

(Unaudited)

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Anadarko Petroleum Corporation

(Unaudited)

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Anadarko Petroleum Corporation

(Unaudited)

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Anadarko Petroleum Corporation

Financial and Operating External Guidance

As of May 2, 2011

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Anadarko Petroleum Corporation

Financial and Operating External Guidance

As of May 2, 2011

*  Excludes Western Gas Partners, LP (WES)

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Anadarko Petroleum Corporation

Commodity Hedge Positions (Excluding Natural Gas Basis)

As of May 2, 2011