In the event a portion or portions of the leased premises is pooled or unitized with other land so as to form a pooled unit or units, operations on, completion of a well upon, or production from such unit or units will not maintain this lease in force as to that portion of the leased premises not included in such unit or units. The lease may be maintained in force as to any portion of the leased premises covered hereby and not included in such unit or units in any manner provided for herein; provided, however, if at the end of the primary term or after the expiration of the primary term, Lessee is then engaged in drilling or reworking operations on the non-unitized portion of the leased premises or on acreage pooled therewith, or if Lessee has completed a well as a producer or a dry hole anywhere on the leased premises or lands pooled therewith within ninety (90) days prior to the expiration of the primary term, this lease shall remain in full force and effect as to all non-unitized acreage so long as Lessee commences drilling operations on the non-unitized portion of the leased premises or on acreage pooled therewith within ninety (90) days of the completion of such well as a producer or a dry hole and conducts continuous operations thereon with no cessation of longer than ninety (90) days between the completion of drilling or reworking operations on a well and the commencement of such operations for the next succeeding well.