Exhibit 99

NEWS

ANADARKO ANNOUNCES 2012 FOURTH-QUARTER

AND FULL-YEAR RESULTS

HOUSTON, Feb. 4, 2013 – Anadarko Petroleum Corporation (NYSE: APC) today announced 2012 fourth-quarter results, reporting net income attributable to common stockholders of $203 million, or $.40 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 $254 million, or $.51 per share (diluted) on an after-tax basis.⁽¹⁾ Cash flow from operating activities in the fourth quarter of 2012 was $2.220 billion. Discretionary cash flow for the quarter totaled $1.612 billion. ⁽²⁾

For the year ended Dec. 31, 2012, Anadarko reported net income attributable to common stockholders of $2.391 billion, or $4.74 per share (diluted), and full-year 2012 cash flow from operating activities was $8.339 billion. Discretionary cash flow for the year totaled $7.157 billion.

2012 OPERATIONAL HIGHLIGHTS

“Anadarko’s outstanding operational results in 2012 demonstrated the flexibility and strength of our capital-efficient portfolio,” said Anadarko President and CEO Al Walker. “We achieved record production, highlighted by a 25,000 barrel-per-day increase in higher-margin liquids sales volumes over 2011, while continuing to safely improve efficiencies in every segment of our business. We achieved a reserve-replacement ratio of 162 percent, before the effects of price revisions, at competitive costs, and we remain on track to meet our goal of 3 billion BOE of proved reserves by the end of 2014. We also made significant progress advancing several large-scale development projects, contributing to our transparent future growth. We delivered a 67-percent success rate in

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2012 from our deepwater exploration and appraisal drilling program, where we’ve had a very strong three-year average success rate of almost 70 percent. The combination of industry-leading deepwater exploration success and strong, capital-efficient operating results gives Anadarko a track record our employees are very proud of and look forward to building upon in 2013.”

2012 SALES VOLUMES AND PROVED RESERVES

Anadarko’s full-year sales volumes of natural gas, crude oil and natural gas liquids (NGLs) totaled a record 268 million BOE, or approximately 732,000 BOE per day, an increase of 8 percent over full-year 2011 sales volumes of approximately 248 million BOE. Fourth-quarter 2012 sales volumes of natural gas, crude oil and NGLs totaled 68 million BOE, or 741,000 BOE per day.

Anadarko added 434 million BOE of proved reserves in 2012, before the effects of price revisions, and incurred oil and natural gas exploration and development costs of $6.358 billion.⁽²⁾ The company estimates its proved reserves at year-end 2012 totaled 2.56 billion BOE, with 74 percent of its reserves in the proved developed category and 26 percent categorized as proved undeveloped. At year-end 2012, Anadarko’s proved reserves were comprised of 46 percent liquids and 54 percent natural gas.

2012 U.S. ONSHORE HIGHLIGHTS

Anadarko’s U.S. onshore operating areas achieved a 28-percent increase in oil sales volumes for the full year relative to 2011. As announced in December, the company achieved gross processed production milestones of 100,000 BOE per day in four core growth plays (Wattenberg, Eagleford, Greater Natural Buttes and Marcellus), and made significant progress to enable future production growth throughout its U.S. onshore portfolio by continuing to expand its large and growing midstream infrastructure.

During 2012, Anadarko increased the net estimated resource potential in the core of its liquids-rich Wattenberg Horizontal play to a new range of 1.0 billion to 1.5 billion BOE, with significant additional potential on the company’s large mineral interest outside the core of the field. The Wattenberg field continues to generate outstanding economics, with rates of return in excess of 100 percent, and delivered sales volumes growth of more than 25 percent over 2011, including a 41-percent increase in oil sales volumes.

In the liquids-rich Eagleford Shale, Anadarko achieved a 93-percent increase in sales volumes and continued to significantly improve drilling and completions performance over 2011. By the end of 2012, drilling cycle times in the field averaged 9.2 days from spud to rig release, representing a 26-

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percent improvement over the fourth quarter of 2011. Other core areas that demonstrated record sales-volumes growth in 2012 included Greater Natural Buttes, Marcellus, Permian oil and the East Texas Horizontal play.

2012 INTERNATIONAL AND DEEPWATER HIGHLIGHTS

In 2012, Anadarko continued a robust worldwide exploration and appraisal program, participating in more than 25 deepwater wells. As previously announced, the company made two new significant natural gas discoveries offshore Mozambique during 2012 at the Golfinho and Atum prospects. These discoveries more than doubled Anadarko’s previous estimated recoverable resources in the operated Offshore Area 1 to a range of 35 trillion cubic feet (Tcf) to 65-plus Tcf. Anadarko also continued its active appraisal drilling and testing programs, the results of which verified the high deliverability of both the Prosperidade and Golfinho/Atum complexes.

The company continued to advance the Mozambique liquefied natural gas (LNG) development toward first sales in 2018. In December, Anadarko reached Heads of Agreement with Eni, establishing foundational principles for the coordinated development of common natural gas reservoirs in Offshore Areas 1 and 4. Anadarko also awarded competitive Front-End Engineering and Design contracts for both the offshore installation and an initial, four-train onshore LNG park.

In West Africa, the company achieved significant exploration and appraisal success in discovering and delineating oil opportunities offshore Ghana and Côte d’Ivoire. In the Deepwater Tano Block offshore Ghana, Anadarko and its partners continued to advance the TEN (Tweneboa, Enyenra and Ntomme) complex by drilling three successful exploration/appraisal wells and submitting a Plan of Development to the Ghanaian government. The partnership also increased production at Jubilee to more than 110,000 barrels of oil per day, through the successful application of acid jobs and the startup of the initial phase-1A drilling program. The company’s Paon discovery offshore Côte d’Ivoire confirmed the extension of the upper Cretaceous fan play and could potentially anchor a new oil development.

The company achieved first oil in March at its Caesar/Tonga mega project in the deepwater Gulf of Mexico and, during the fourth quarter, drilled another successful development well in the field. Anadarko advanced its Heidelberg discovery by ordering long-lead items and expects to seek project sanction by mid-year 2013. In addition, the company drilled its first development well at its sanctioned Lucius development, encountering 910 net feet of oil pay.

In 2013, Anadarko is continuing its active international and deepwater drilling program with exploration, appraisal, completions and development activities under way in the Gulf of Mexico.

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Internationally, Anadarko recently spud the first of two wells offshore Kenya, and expects to achieve initial oil production during the first quarter of 2013 from the first of three facilities in the El Merk complex in Algeria.

2012 FINANCIAL HIGHLIGHTS

“Anadarko further strengthened its balance sheet during 2012 by repaying all borrowings under its revolving credit facility and improving the company’s net-debt-to-adjusted-capitalization⁽²⁾ ratio from 41 percent at year-end 2011 to 34 percent at year-end 2012,” Walker said. “We ended the year with $2.5 billion of cash on hand, bolstered by the collection of $1 billion associated with the Algeria exceptional profits tax resolution. During the year, we actively managed our portfolio through various monetizations that accelerated significant value for our shareholders. Among these monetizations were the previously announced Lucius and Salt Creek carried-interest agreements, as well as a $114 million transaction for approximately 59,000 acres south of our core Wattenberg activity, while retaining a 20-percent royalty interest on our fee mineral acreage. We were also very pleased with the initial public offering of WGP, which established a current market value of more than $6.5 billion for Anadarko’s remaining 91-percent interest. Value acceleration will continue to be a priority for us in 2013, as demonstrated by the recently announced divestiture of our equity interest in the OCI soda ash business for $310 million and additional potential consideration.”

Anadarko generated $852 million of adjusted free cash flow⁽²⁾ during the year, which includes the impact of $529 million of capital expenditures incurred by Western Gas Partners, LP (NYSE: WES).

Anadarko plans to communicate its 2013 capital program and performance expectations during an Investor Conference Call, scheduled for Feb. 20, 2013.

OPERATIONS REPORT

For more details on Anadarko’s 2012 operations, please refer to the operations report on fourth-quarter 2012 activity. The report is available at www.anadarko.com on the Investor Relations page.

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CONFERENCE CALL TOMORROW AT 9 A.M. CST, 10 A.M. EST

Anadarko will host a conference call on Tuesday, February 5, at 9 a.m. Central Standard Time (10 a.m. Eastern Standard Time) to discuss fourth-quarter and full-year results. The dial-in number is 855.812.0464 in the United States or 970.300.2271 for international calls. The confirmation number is 69777651. 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 website for approximately 30 days following the call.

FINANCIAL DATA

Seven pages of summary financial data follow, including proved reserves, costs incurred and the company’s current hedge positions.

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

⁽²⁾ See the accompanying tables for reconciliations of GAAP to non-GAAP financial measures and a statement indicating why management believes the non-GAAP 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 2012, the company had approximately 2.56 billion barrels-equivalent of proved reserves, making it one of the world’s largest independent exploration and production companies. For more information about Anadarko and APC Flash Feed updates, 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 finalize year-end reserves, drill, develop and commercially operate the drilling prospects identified in this news release, continue to coordinate development activities with Eni in Mozambique, successfully plan, secure necessary government approvals, finance, build and operate an LNG project and WGP’s market performance and the impact on Anadarko’s ownership interest. See “Risk Factors” in the company’s 2011 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.

Cautionary Note to U.S. Investors: The United States Securities and Exchange Commission (“SEC”) permits oil and gas companies, in their filings with the SEC, to disclose only proved, probable and possible reserves that meet the SEC’s definitions for such terms. Anadarko uses certain terms in this news release, such as “net estimated resource potential,” “estimated recoverable resources,” and similar terms that the SEC’s guidelines strictly prohibit Anadarko from including in filings with the SEC. U.S. investors are urged to consider closely the disclosure in Anadarko’s Form 10-K for the year ended Dec. 31, 2011, File No. 001-08968, available from Anadarko at www.anadarko.com or by writing Anadarko at: Anadarko Petroleum Corporation, 1201 Lake Robbins Drive, The Woodlands, Texas 77380, Attn: Investor Relations. This form may also be obtained by contacting the SEC at 1-800-SEC-0330.

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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

Christina Ramirez, christina.ramirez@anadarko.com, 832.636.8687

INVESTORS:

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

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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 (non-GAAP), free cash flow (non-GAAP), and adjusted free cash flow (non-GAAP), as well as 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 because it is useful in comparisons of oil and gas exploration and production companies as it excludes fluctuations in assets and liabilities. Management uses free cash flow and adjusted free cash flow to demonstrate the Company’s ability to internally fund capital expenditures and to service or incur additional debt. 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

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