Abstract: A well tool apparatus having a perforating section at its lower end has an upper section comprised of a reservoir containing a compatible perforating fluid and a pump for pumping such fluid down through the perforating section and out the lower end of the apparatus. A protective shield containing a sand control medium is provided for causing the perforating fluid to displace the well bore fluid in the region along the length of the perforating section, such displaced fluid being recaptured above a floating piston in the reservoir containing the perforating fluid. Means are provided for releasing the compatible perforating fluid into the annulus between the shield and the perforating section, the lower end of the shield having a gravel screen and a port for releasing the perforating fluid into the annulus between the apparatus and the casing to be perforated. Upon perforating, the sand control medium settles into place inside the shield to provide sand control for the formation being produced.