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Jan 12 (Reuters) - Oil and gas producer Anadarko Petroleum Corporation said on Thursday it would sell its Eagleford Shale assets in South Texas for about $2.3 billion to a strategic 50/50 partnership formed by Sanchez Energy Corporation and asset manager Blackstone Group LP.

Al Walker, chief executive officer of Anadarko, said in a statement that the sale would help the company accelerate operations in its more high-return properties such as Texas' Delaware Basin, the DJ Basin in Colorado and the deepwater Gulf of Mexico.

The divestiture includes about 155,000 net acres mainly located in Dimmit and Webb counties.

Sales volumes from these assets totaled about 45,000 barrels of liquids per day (bpld) and roughly 131 million cubic feet of natural gas per day at the end of the fourth-quarter

The company's master limited partnership, Western Gas Partners LP, would continue to own and operate its midstream assets in South Texas, Anadarko said.

Anadarko announced in December the sale of certain natural gas assets in the Marcellus shale for about $1.24 billion to a unit of Alta Resources Development LLC.

The company said the transaction was expected to close in the first quarter of 2017.

Andarko shares were little changed in extended trading.

Intrepid Partners served as financial adviser to Sanchez Energy, and its legal advice was provided by Akin Gump Strauss Hauer & Feld LLP and Kirkland & Ellis LLP.

Kirkland & Ellis served as legal advisor and Jefferies & Company Inc served as the financial advisor to Blackstone.

(Reporting by Vishaka George in Bengaluru; Editing by Andrew Hay and Cynthia Osterman)