OK003 – Pneumatic Fracturing
Federal Government Facility – Oklahoma City, Oklahoma
Pneumatic Fracturing (PF) was used to enhance the rate of #2 fuel oil recovery in a sandstone/shale formation at a military facility in Oklahoma City, Oklahoma. The free product was trapped in porous layers beneath fine textured confining zones and beneath a decommissioned UST. Several recovery wells had been installed in the vicinity of the closed tank, but the recovery rates were very low. A single pneumatic injection was applied adjacent to the tank at a depth between 26 and 28 ft. to increase the yield of the free product.
The project was conducted under a DOE & DOD grant in conjunction with the Hazardous Substance Management Research Center. Additional application of the technology occurred at the site in 1995. Results showed that Pneumatic Fracturing provided direct access to the trapped oil, as was observed during static conditions. Prior to fracturing, oil in a recovery well eight feet from the fracture well would reach static conditions after approximately 300 hours with 1.5 ft. of free product floating on the water table. Following the application of Pneumatic Fracturing, equilibrium was attained in only 80 hours when the well contained 20.2 ft. of free product. Pump system operations, including additional recovery wells, further showed the increased rate of product recovery. During the 17 months prior to Pneumatic Fracturing, the system averaged 155 gallons of free product recovered per month. Following the application of Pneumatic Fracturing, the rate increased to 435 gallons per month. The total amount of free product recovered in seven months following the Pneumatic Fracturing application surpassed the total product recovered over the life of the system in the previous 17 months.
Pneumatic Fracturing also increased the ratio of oil to water recovered from the formation. During pre-fracture pumping, the product represented only an average of 12% of the total fluid recovered. Following Pneumatic Fracturing application, oil contributed to 74% of the total fluids recovered. This reduced water treatment costs tremendously.
Following this successful application, Pneumatic Fracturing was applied at three newly installed wells. The objective for this project was to access the #2 fuel oil trapped in the sandstone/shale formation at other portions of the site where the free product had been detected but recovery operations had been ineffective. Two of these wells were located within 15 ft. of an active parts cleaning and storage building. The project was completed in February of 1995.
During this second application, Pneumatic Fracturing was observed to increase the oil production in wells as far as 59 ft. away from the closest fracturing point. The first order rate constant, which is a measurement of the rate at which oil enters the well, was found to increase 434% at one recovery well 7 ft. from fracture point, and 224% at another recovery well 8 ft. from the closest fracture point. The production in oil per day from the first recovery well increased over five fold from 1.2 gallons per day to an average of 6.2 gallons, including a peak recovery rate of 8.4 gallons per day. During Pneumatic Fracturing applications, observations were made to determine whether the building was affected by the process. Pneumatic Fracturing was not observed to permanently affect the building structure. Minor movement of the structure below safety criteria was observed, with evidence of pneumatic connection at wells located 115 ft. underneath the building.
1. Pneumatic Fracturing Speeds Remediation
– David E. Mizell and Daniel P. Hunt
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