FL001 – Pneumatic Fracturing
Service Station, Florida
Figure 1: Using an external nitrogen bulk supply the entire project was completed within five days.
Pneumatic Fracturing (PF) was applied at a gasoline service station in Tallahassee, Florida. The geology consisted of a montmorillonite clay with interbedded sands. A prominent clay layer was present at a depth of approximately fifteen to twenty-seven feet below grade. Contaminants, including benzene, toluene, ethylbenzene and xylenes (BTEX) were found in the subsurface soils in the tank area of the site. Prior to ARS’ involvement, the dual-phase extraction system was only effective at removing contaminants from the interbedded sand layers, but not from the clay zones. Pneumatic Fracturing was selected to target the clay zone and increase the zone’s bulk permeability by creating a fracture network within the clay.
Figure 2: PF injections applied adjacent to the pump station
A post-fracture extraction test on one of the extraction wells showed good influence in nearby monitoring wells and resulted in soil vapor concentrations increasing from less than 1ppm to more than 1000ppm. The results from field observations and analysis of recorded pressure data supported the formation of an interconnected fracture network within the treatment zone. During post-injection permeability testing, significant pressure influence was observed 19 ft. from the fracture well. The pre-injection levels at this distance were zero. Pneumatic Fracturing resulted in the production of a viable network of fractures that enhanced the recovery of hydrocarbons at the site. After fracturing seven additional wells at the site, the client installed a dual-phase extraction system for the site-wide extraction.
- Fuhr, Joseph M., Liskowitz J.J, (1998) Enhancing Hydrocarbon Recovery in a Low Permeability Montmorillonitic Clay Through Pneumatic Fracturing, AEHS, East Coast Conference on Soil and Sediment Issues, Amberst, MA.