Selectively perforating and treating a cased well

Claim 1

A process for forming and individually treating perforations at different depths within a depth interval to be perforated in a cased well, which process comprises: positioning a conduit within the well casing and displacing a fluid of selected composition into the passageway between the conduit and the casing within the depth interval to be perforated; above the depth interval to be perforated, sealing the passageway between the conduit and the casing with a slidable mechanical seal that is located above the lower end portion of the conduit and is adapted to maintain said seal around the conduit while the conduit is moved to adjust the position of its lower end; while maintaining said slidable seal, moving the conduit to the extent required to position its lower end above the top depth to be perforated; mechanically sealing the passageway around the lower end of the conduit, between the lower end portion of the conduit and the adjacent portion of casing; while maintaining said seal around the lower end of the conduit, operating a perforating device and a fluid circulating device to form and fluid-treat at least one perforation at substantially the top depth to be perforated; and moving the conduit, sealing the passageway around the lower end of the conduit, and maintaining such a seal while operating a perforating device and fluid-circulating means, at least one additional time, in order to form and treat at least one perforation at a different depth within the same depth interval.