Royal Dutch Shell PLC says that after several setbacks, it no longer plans to try to drill deep enough to reach oil in exploratory wells off the coast of Alaska this year.

The company was granted two exploratory drilling permits by the U.S. government after a long struggle with environmentalists who say seeking oil in the icy waters is too risky. Shell now says it is scaling back ambitions until next summer, after one of its containment systems failed during a test. Earlier, the company delayed drilling due to ice floe movements.

The company says that in the time remaining this season it plans to drill shallow “top holes” for wells that may be further pursued in coming years.

Shell is seeking oil in the Chukchi and Beaufort Seas.