The Houston company already has a $33 billion deal in place with Chevron. : Anadarko Petroleum is reopening acquisition talks with Occidental Petroleum — two weeks after agreeing to sell itself to Chevron — setting up a possible faceoff over its prized shale oil assets in the Permian Basin. “Anadarko’s board of directors, following consultation with its financial and legal advisers, has unanimously determined that the Occidental proposal could reasonably be expected to result in a ‘superior proposal’ as defined in the Chevron Merger Agreement,” the Houston-based company said Monday in a statement.