15. Notwithstanding anything to the contrary, it is agreed that should Lessee exercise his option to pool or combine any portion of the land covered hereby with other lands, lease or leases as hereinbefore provided, then such operations and production on and in any such pooled unit as herein provided, shall continue this lease in force and effect during or after the primary term as to that portion of the lands covered by this lease, included in such unit or units as hereinabove provided, but not as to such portion of said lands covered by this lease and not included in any such unit. This lease maybe kept in force and effect as to such remainder in any manner elsewhere provided in this lease not inconsistent with this paragraph.