High Energy Gas Frac

Abstract

A High Energy Gas Frac field test has been conducted at DOE's Nevada Test Site, Nevada. The Gas Frac utilizes a controlled propellant deflagration to initiate and extend multiple fractures in a borehole. Three different propellants were tested in a volcanic ash fall tuff medium and resulted in phenomenologically different behavior. Mineback of the experiments provided direct observational evidence to characterize the results. The slowest propellant (burn time = 0.9 s) had a pressure loading rate (0.09 psi/..mu..s) and a peak pressure (6250 psi) that were relatively low and resulted in a single fracture that was similar in appearance to a hydraulic fracture. The fast propellant (burn time approx. 1 ms) had a pressure loading rate (> 1500 psi/..mu..s) and a peak pressure (> 20,000 psi) that were so large that, although multiple fractures were initiated, considerable crushing near the wellbore was observed and only one fracture was extended more than 6 in. from the wellbore. The intermediate propellant (burn time = 9.4 ms) had a pressure loading rate (20 psi/..mu..s) and a peak pressure (13,800 psi) sufficient to initiate and extend 12 separate fractures in random radial directions. Lengths of these fractures varied from 6 in. to 8 ftmore » for 20 lb of propellant in an 8 in. borehole. This technique provides an attractive method to alleviate wellbore damage for other in situ technology applications. « less

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