“The most expensive part of abandoning a well is returning the surface lease back to the way you found it before drilling started,” says retired rig manager Dan Claypool. “In a remote location, a long road that was used for 50 years could have gravel driven ten feet into the ground by heavy trucks.” Digging that up is why some abandonments cost up to $300,000, he says. Surface abandonment also includes removing the wellhead.
Full abandonment includes both surface and downhole work. Zone abandonment means formally abandoning a producing zone and going up-hole to produce above it. A bridge plug—a packer— saddles across the well to take pressure off the wellhead. The cement plug above the producing zone and casing perforations protects the bridge plug. A corrosion inhibitor is added to the water that fills up the bore below the plug.
Well abandonment is covered by AER’s Directive 020 Well Abandonment Guide. Typical steps to abandon a well also include checking the cement outside the casing, using a cement log bond. If groundwater protection is required or if the well is leaking (normally methane), remedial repairs are also needed.