DES MOINES — A Texas-based company has asked Iowa regulators for permission to immediately start work on most of the Bakken oil pipeline route through 18 Iowa counties. Dakota Access LLC, a unit of Energy Transfer Partners of Dallas, said in a filing Thursday the work must begin this month to complete the project in one construction season. Pipeline opponents promise to fight the request. The Iowa Utilities Board has approved pipeline plans but said construction can’t begin until federal permits are approved.