Injection/isolation tool

A downhole tool is described which can be used for injection of waste fluids which have been separated from desired production fluids into a disposal formation. When desired, the conduit for the waste fluids to the disposal formation can be closed off, thereby isolating the disposal formation from the production zone and providing access selectively to the production zone. The downhole tool includes an inner tube having a bore and being connectable at each end to a tubing string; an outer tube having a outer surface and being disposed about and spaced from the inner tube; an annulus between the inner tube and the outer tube; upper and lower openings from the outer surface of the outer tube to the annulus; an upper well sealing means disposed on the outer tube below the upper opening for providing an annular seal between the casing and the outer tube; a lower well sealing means disposed on the outer tube above the lower opening for providing an annular seal thereabout; a transverse port positioned on the tool between the upper well sealing means and the lower well sealing means, the transverse port extending to provide access between the bore of the inner tube and the outer surface of the outer tube without opening into the annulus; and a means for opening and closing the transverse port.