The obligation or liability of each working interest owner in the several separately owned tracts in the unit for the payment of unit expense at all times shall be several and not joint or collective, and a working interest owner shall not be chargeable with, obligated or liable for, directly or indirectly, more than the amount apportioned, assessed or otherwise charged to his interest in the separately owned tract pursuant to the order of unitization.
NMS § 70-7-15