THE STRUCTURE OF THE SLEEVE PIPE
Sleeve pipes are injection pipes made from hard PVC or stained steel with diameters of 1” to 2″ (3 cm), which are perforated at intervals of 1 foot (33 cm).The opening is covered with a rubber sleeve that expands in the form of a valve under the injection pressure, allowing the oxidant to permeate through the perforation into the surrounding area.
Each sleeve can be approached with a double packer precisely. The double packer consists of 2 expandable packer dealings with an outlet pipe between them. Attached to the double packer is the injection tube.
Due to the pressure controlled injection a high horizontal penetration of the oxidizer is achieved with ISCORAPID. It is very effective in low permeable soil zones.
The ISCORAPID procedure
A borehole with the diameter of 5-6 inches is drilled either with auger or core drilling. Casing is only necessary if the soil does not stay open.
Installation of the sleeve pipes. For high depths centralizers will be used to fix the pipe.
The annular space is sealed with cement suspension using a tremie pipe. Duration of the cement hardening is 3 days.
After sealing the annular space a double packer is brought into the sleeve pipe.
After the cement suspension has hardened, it forms a sheathing around the pipe. This fixes the sleeve pipe in its position and prevents the fluid from rising into the annular space. During injection, the cementation at the perforated areas of the sleeve pipe is broken up by water. The cementation around the pipe is being cracked with a pressure of about 1200 psi (80 bar).
After expanding the rubber sleeves the reagent is injected with a pressure of 50 up to 200 psi. The expansion of the double packer’s sealing sleeves can be reversed by reducing the pressure. The packer can be moved within the sleeve pipe so that the injection can be controlled and repeated as many times as required at every sleeve.