California Code, Public Resources Code - PRC § 3728

Any individual or blanket indemnity bond issued in compliance with this chapter may, with the consent of the supervisor, be terminated and canceled and the surety be relieved of all obligations thereunder when the well or wells covered by such bond have been properly abandoned or another valid bond has been substituted therefor.  Should the person who has filed a blanket bond properly abandon a portion of his wells covered by the bond, the bond may, with the consent of the supervisor, be terminated and canceled and the surety be relieved of all obligations thereunder upon the filing by such person of an individual bond for each well which he is still engaged in drilling, redrilling, deepening, maintaining, or abandoning.  Liability as to individual wells that have been drilled and abandoned under a blanket bond may also be terminated with the consent of the supervisor.