Cal. RTC § 2189.5

Every tax on personal property and improvements, located upon or appurtenant to a leasehold estate for the production of gas, petroleum or other hydrocarbon substances from beneath the surface of the earth, and belonging to the owner of the leasehold estate, may be secured by the leasehold estate, when, in the opinion of the assessor, the leasehold estate is of sufficient value to constitute security for the payment of all taxes upon that personal property or improvements and upon that leasehold estate. In the event of delinquency in the payment of that tax, the personal property, improvements, and leasehold estate shall be subject to seizure and sale in the same manner as provided for the seizure and sale of unsecured personal property, in Sections 2951 to 2962, inclusive, at any time within three years after the delinquency. Suit may be brought against an assessee of those taxes in the event of delinquency in the payment thereof.

If the tax thereon remains unpaid at the time set for the declaration of default for delinquent taxes, the tax together with any penalty and costs as may have accrued thereon while on the secured roll shall be transferred to the unsecured roll.

Those taxes that are delinquent at the time the amendment to this section, enacted at the 1973–74 Regular Session, goes into effect may also be transferred to the current unsecured roll.