5 ILCS 615/20

All leases shall provide that the lessee shall drill an offset well to any well on adjoining land which is within three hundred fifty (350) feet of any outer boundary of the land covered by the lease, and which well on adjoining lands is producing petroleum in paying quantities and draining the lands covered by the lease, such offset to be begun within ninety (90) days from the completion of the adjoining well and drilled with due diligence to completion.