Subject to such reasonable limitations as may be set out in the plan of unitization, the unit shall have a first and prior lien upon the leasehold estate and other oil and gas rights (exclusive of a one-eighth royalty interest or exclusive of the interest provided in the unit operating plan which allocates costs, if it is different than one-eighth) in and to each separately owned tract, the interest of the owners thereof in and to the unit production and all equipment in the possession of the unit, to secure the payment of the amount of the unit expense charged to and assessed against such separately owned tract.
NMS § 70-7-14