Patent ID: 8272441

Claim:
A system for positioning a downhole service tool in the interior of a pipe string, said system comprising: a. a plurality of tubular sub-sections distributed between selected pipe joints in a pipe string length comprising a plurality of pipe joints joined coaxially from a first to second end thereof, each sub-section having a bore substantially coaxial with a bore of said pipe string and a substantially circular aperture in a cross-section of said bore with an inside diameter distinctive to each sub-section, means for securing at a respective immovable position along the axis of said pipe string each aperture of said plurality of sub-sections, said distinctive aperture diameters diminishing incrementally by successive positions from said first to second ends: and,: b. an axially elongated tool assembly including a downhole service tool disposed for independent transport along a said pipe string bore, said tool assembly having a cross-sectional profile adapted to engage a specific one of said apertures with a fluid pressure seal to isolate a first end pipe string bore from a second end pipe bore, said tool assembly including a fluid pressure actuated valve to selectively by-pass said specific aperture with fluid flow in a direction from said first end toward said second end.