An Alberta oilsands company has been ordered to abandon its operations after repeatedly failing to address a string of problems — including cracked pipelines, leaking tanks and other critical repairs — over almost three years.

The abandonment order, issued this week by the Alberta Energy Regulator against Sunshine Oilsands Ltd., said its operations pose a risk to public and environmental safety and must be fully decommissioned. Sunshine operations include a long list of well sites in the Athabas…