Combining technologies for an effective seal
To optimally drill and complete a leak-free UGS well, GASAG contacted
Schlumberger and selected a combination of FUTUR self-healing cement and
FlexSTONE flexible cement to provide two barriers to prevent gas migration to
FlexSTONE cement was designed to withstand pressure and temperature
fluctuations during injection and production phases, providing the primary
barrier against unwanted gas migration by preventing cracks from forming.
FUTUR self-healing cement provided a secondary barrier against leaks.
When hydrocarbons come into contact with the FUTUR sealant, it responds by
swelling to close gaps and flow paths. Within hours, the cracks or fissures are
healed and the hydraulic seal is reestablished. FUTUR cement can be
strategically placedfrom surface to reservoir depth, in any string of the
well to distribute an effective long-term seal throughout the well. It
continues to reseal whenever annular integrity is compromised.
Ensuring well integrity now and in the future
Once the cement was placed, it was evaluated using a cement bond log
ultrasonic imager tool. The logs showed an optimal cement bonding across the
treated interval, ensuring that cement placement was successful. Because no
remedial cementing job was required, 3 days of rig time were saved. In
addition, FUTUR cementing technology will be able to react efficiently and
selfrepair if the cyclical injection and production stresses cause a loss of
The excellent results for the well prompted the operator to drill and
cement a second well using FUTUR technology.