Mont. Code Ann. § 77-4-123

If geothermal resources are not being produced from the leased premises at the expiration of the primary term of the lease but the owner of the lease is then engaged in drilling on the premises for geothermal resources, then the lease term shall be extended for so long as the drilling operations are diligently continued. If geothermal resources are recovered from any well drilled after the expiration of the primary term, the lease shall continue in force so long as geothermal resources in paying quantities are produced from the leased premises.