Many clients prefer top-down injection for reasons of controlled and directed transport of the fluids and slurries. We do agree with the reasons but do not like the practical difficulties of top-down injection. We often use a special injection tool that allows a bottom-up approach but with top-down precision; stronger, our injection tool shows better results as the interface with the geological formation is a lot better. The key for the succes of this tool is downward locking of the borehole while extracting slowly when pumping the fluids and slurries.
Top three images showing our injection tool. The tool is driven down in closed position with our geoprobe. At depth pumping is started while retracting the rod string; hence the screen is exposed and has a 60 cm interface with the geological formation. The 30 cm tip is attached to the screen and locks the borehole downwards.
The bottom image shows the standard geoprobe injection tool with limited contact with the formation via 4 injection ports rather then the 120 we use.