which has an upper end 32 and a lower end 34 a packer and a hanger 36 are set in lower end 20 of casing 14 and sealingly position an upper end 42 of an isolation string 40 in casing 14 a base open hole packer 38 is positioned in a lower portion of the uncased wellbore to support isolation string 40 at its lower end 44 a seal assembly 46 is positioned on packer 38 to sealingly position isolation string 40 in uncased portion 30 a lower extension 48 of isolation string 40 is used to position the valves and screens used for the treatment of each production interval at a desired position in the production interval to be treated a similar pipe 100 is used in the upper portion of isolation string 40 to position it relative to lower end 20 of casing 14 while not shown isolation string 40 may include pipe spacer sections between each section of isolation string 40 to position the sections 86 88 90 and 92 for treating the production intervals in the production intervals 22 24 26 and 28 as shown isolation string 40 includes a first section 86 a second section 88 a third section 90 and a fourth section 92 in each production interval a similar arrangement is used for the treatment of the production interval the treatment is shown in some detail in fig1 for.