“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.

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