Cal. Pub. Res. Code § 3721

Every owner or operator of any well shall designate an agent, giving his or her address, who resides in this state, to receive and accept all orders, notices, and processes of the supervisor or any court of law. Every person so appointing an agent shall, within five days after the termination of the agency, notify the supervisor, in writing, of such termination, and unless operations are discontinued, shall appoint a new agent.