Anadarko Petroleum Corporation is selling for US$4.015 billion basically all of its remaining midstream assets to Western Gas Partners, a master limited partnership formed by Anadarko a decade ago to own, develop, and operate midstream assets.   Anadarko will receive US$2.0075 billion of the transaction proceeds in cash, while the remainder to be paid in new Western Gas equity, Anadarko said in a statement on Thursday. Anadarko’s remaining midstream assets subject to the sale are largely associated with Anadarko’s two key U.S.…