Abstract: An elongated tubular assembly is provided defining a longitudinal central passage therethrough. Longitudinally spaced opposing packer structures are carried by and extend about the exterior of the tubing assembly and the latter includes a bypass passage extending therealong, independent of the central passage, opening at its opposite ends to the exterior of the tubular assembly on the remote sides of the packer structures. The tubular assembly further includes generally radial perforation wash fluid passages opening inwardly into the central passage at their inner ends and outwardly of the exterior of the tubular assembly intermediate the packer structures. The tubular assembly is disposed in a tubing string immediately above a full opening and full closing tubing section disposed therebelow and supporting a drag block at its lower end and the tubular assembly is disposed immediately below a selectively openable and closable fluid bypass tube section disposed thereabove.