A vertical Pugh Clause could provide a lease to a particular depth, such as 100 feet below the drilled well. The lessee would be limited to drilling to 100 feet but no further. Conceivably, the lessor could lease property below that range to another entity.
In general terms, the Pugh Clause provides that production from a unitized or pooled area located on or including a portion of the leased lands will not be sufficient to extend the primary term for the entire leasehold.