SOUTH PORTLAND — Residents here are weighing the impact of Thursday’s announcement by TransCanada Corp. that it has abandoned plans to build the controversial Energy East Pipeline, which would have carried 1.1 million barrels of crude oil per day from western Canada to the Atlantic coast. It wasn’t immediately clear whether TransCanada’s decision might increase or decrease the need to export Canadian oil through an existing pipeline that runs from refineries in Montreal to waterfront terminals in South Portland. The Portland Pipe Line Corp.