Abstract: In the representative embodiment of the invention described herein, formation-treating apparatus is adapted to be dependently supported in a well bore from a pipe string and which includes upper and lower telescoped body members adapted to be selectively moved between upper and lower operating positions for controlling the injection of treating fluids into one or more earth formations traversed by the well bore. A pair of spaced packer elements are mounted on the lower member above and below a discharge port and cooperatively arranged for isolating a well bore interval that is to be treated by discharging one or more treating fluids in the pipe string from the port. To control the injection of treating fluids, retrievable valve means are also cooperatively arranged within the body members and adapted to be alternatively seated on upper and lower full-bore valve seats in the upper and lower bodies in response to movement of the bodies to their operating positions.

Abstract: In the representative embodiment of the apparatus of the invention disclosed herein, a packer plug is arranged with sealing means for closing off the central bore of the mandrel of a packer that is set in a well bore for selectively isolating upper and lower formation intervals. When the plug is set in the packer mandrel, collet fingers on the body of the new and improved plug for threadedly engaging internal threads in the upper end of the packer mandrel. To secure the plug against unwanted release, a retainer member is cooperatively secured to the plug mandrel by a shear pin which will fail only at a predetermined force.