HOUSTON — Faced with continued regulatory delays, Royal Dutch Shell announced on Thursday that it was abandoning plans to drill for oil in Alaskan Arctic waters this year but that it remained committed to exploring in the area in the future. Shell has already invested $3.5 billion to drill in Alaska's Beaufort and Chukchi Seas, but the company has been snarled in regulatory delays and lawsuits since it entered into 10-year exploration leases five years ago. The latest hurdle is obtaining an air quality permit from the Environmental Protection Agency, which has been delayed by an E.P.A. appeals panel that recently ruled that it wanted a more thorough review of the impact diesel emissions from exploration might have on local indigenous communities. Shell had been urging the government to make a quick determination, since the company would need some time to get equipment in place to drill next summer when the water is free of ice. Moving the equipment and other preparations would cost more than $100 million.