EXHIBIT 21

LIST OF SUBSIDIARIES ⁽¹⁾

At December 31, 2012

Anadarko (S.L.) Company

a Cayman Islands corporation,

Anadarko 20-11 Company

a Cayman Islands corporation,

Anadarko 20-13 Company

a Cayman Islands corporation,

Anadarko 20-18 Company

a Cayman Islands corporation,

Anadarko 20-22 Company

a Cayman Islands corporation,

Anadarko 20-4 Company

a Cayman Islands corporation,

Anadarko Algeria Company LLC ⁽²⁾

a Delaware limited liability company,

Anadarko Brazil Investment I LLC

a Delaware limited liability company,

Anadarko Development Holding Ltd.

a Gibraltar limited liability company,

Anadarko E&P Company LP ^{(2) (3)}

a Delaware limited partnership,

Anadarko Energy Holding Ltd.

a Gibraltar limited liability company,

Anadarko Energy Marketing, Inc.

a Delaware corporation,

Anadarko Energy Services Company ⁽²⁾

a Delaware corporation,

Anadarko Exploracao e Producao de Petroleo e Gas Natural LTDA.

a Brazil limited liability company,

Anadarko Ghana Mahogany-1 Company

a Cayman Islands corporation,

Anadarko Global Energy SARL ⁽²⁾

a Luxembourg limited liability company,

Anadarko Global Funding 1 Company

a Cayman Islands corporation,

Anadarko Holding Company ⁽²⁾

a Utah corporation,

Anadarko International Development SARL

a Luxembourg limited liability company,

Anadarko Land Corp

a Nebraska corporation,

Anadarko Limited Resources LLC

a Delaware limited liability company,

Anadarko Marcellus Midstream, L.L.C.

a Delaware limited liability company,

Anadarko Mauritius Holdings Limited

a Mauritius corporation,

Anadarko Midkiff/Chaney Dell LLC

a Delaware limited liability company,

Anadarko Mozambique Area 1, Limitada Home

a Mozamique limited liability company,

Anadarko Offshore Holding Company, LLC

a Delaware limited liability company,

Anadarko Petroleum Corporation ⁽²⁾

a Delaware corporation,

Anadarko Realty Company

a Texas limited liability company,

Anadarko Uintah Midstream, LLC

a Delaware limited liability company,

Anadarko US Offshore Corporation ⁽²⁾

a Delaware corporation,

Anadarko Venezuela Company

a Cayman Islands corporation,

Anadarko Venezuela LLC

a Delaware limited liability company,

Anadarko WCTP Company

a Cayman Islands corporation,

Anadarko West Texas LLC

a Delaware limited liability company,

Anadarko Worldwide Holdings CV ⁽²⁾

a Netherlands limited partnership,

APC International Holdings LLC

a Delaware limited liability company,

Big Island Trona Company

a Delaware corporation,

Bitter Creek Coal Company

a Utah corporation,

Headwater LLC

a Delaware limited liability company,

Howell Corporation

a Delaware corporation,

Howell Petroleum Corporation

a Delaware corporation,

Kerr-McGee China Petroleum LTD.

a Bahama Islands limited liability company,

Kerr-McGee Corporation ⁽²⁾

a Delaware corporation,

Kerr-McGee Energy Services Corporation

a Delaware corporation,

Kerr-McGee Gathering LLC

a Colorado limited liability company,

Kerr-McGee Oil and Gas Onshore LP ⁽²⁾

a Delaware limited partnership,

Kerr-McGee Onshore Holding LLC ⁽²⁾

a Delaware limited liability company,

Kerr-McGee Shared Services Company LLC ⁽²⁾

a Delaware limited liability company,

Kerr-McGee Worldwide Corporation ⁽²⁾

a Delaware corporation,

KM BM-C Seven Ltd. ⁽²⁾

a Bahamas limited liability company,

KM Denmark Overseas ApS

a Denmark corporation,

KM Global LTD.

a Delaware corporation,

KM Investment Corporation ⁽²⁾

a Nevada corporation,

Lance Oil & Gas Company, Inc.

a Delaware corporation,

Mountain Gas Resources LLC

a Delaware limited liability company,

Resources Holding Inc. ⁽⁴⁾

a Delaware corporation,

Rock Springs Royalty Company LLC

a Utah limited liability company,

Springfield Pipeline LLC

a Texas limited liability company,

Upland Industries Corporation

a Nebraska corporation,

Venezuela US SRL

a Barbados limited liability company,

Western Gas Equity Partners, LP

a Deleware limited partnership,

Western Gas Partners, LP

a Deleware limited partnership,

Western Gas Resources, Inc. ⁽²⁾

a Delaware corporation,

WGR Asset Holding Company LLC

a Delaware limited liability company,

WGR Operating, LP

a Delaware limited partnership,

WHL, Inc. ⁽²⁾

a Delaware corporation

⁽¹⁾  The names of certain subsidiaries have been omitted since, considered in the aggregate as a single subsidiary, they would not constitute a significant subsidiary, as of the end of the year covered by this report, as defined under the Securities and Exchange Commission Regulation S-X 210.1-02(w).

⁽²⁾  Subsidiary meets the conditions of a significant subsidiary under the Securities and Exchange Commission Regulation S-X 210.1-02(w).

⁽³⁾  Effective January 1, 2013, this subsidiary converted to a Delaware limited liability company and changed its name to Anadarko E&P Onshore LLC.

⁽⁴⁾  Effective January 1, 2013, this subsidiary merged into Anadarko Holding Company.