A well casing assembly comprises a length of line having two packer/seal assemblies at the upper end thereof and two packer/seal assemblies at the lower end thereof. The lower end packer/seal assemblies are inverted relative to the upper end packer/seal assemblies. By appropriate design of the setting elements of the packer/seal assemblies, each is selected to have a different setting force. Accordingly, when the tool is set by longitudinal compression thereof, the packer/seal assemblies set in a pre-determined sequence. The packer/seal assemblies are preferably of the type in which an annular slip is expanded by means of a swage. Variations in the setting force may be obtained by variations in material characteristics and/or thickness or by variations in the swage ramp angle, or by any other suitable means.