Longtime shale boss and North Texas energy magnate Scott Sheffield said he’s no longer interested in joining Exxon Mobil Corp.’s board after the U.S.

Chevron has prevailed against Exxon Mobil in a dispute over Hess Corporation’s offshore oil assets in the South American nation of Guyana.

The FTC has reopened an order involving Chevron’s proposed acquisition of Hess, and another regarding Exxon Mobil’s proposed purchase of Pioneer Natural Resources after its initial complaints failed to plead any antitrust law violation.

Oil major Exxon Mobil bought Mars crude for August delivery, two sources said on Wednesday, after briefly halting purchases of the flagship offshore grade due to a zinc contamination issue.