Notwithstanding anything herein contained to the contrary, unless otherwise agreed to in writing by Lessor, there shall be no pooling for oil hereunder until such time as there remains an insufficient amount of leased premises available to support the drilling of and production from an oil well in accordance with governmental spacing requirements. In such event, said insufficient amount of the leased premises not previously allocated to a well or wells may be pooled in accordance with the provisions of this lease. Lessor's consent herein shall not be unreasonably withheld.