In Situ Evaluation Of Several Tailored-Pulse Well-Shooting Concepts

This paper describes a series of five full-scale tests performed to evaluate various multi-frac concepts. The tests were conducted at the Nevada Test Site in cased, horizontal boreholes drilled in ash-fall tuff from a tunnel under 430 m of overburden. This site provides both realistic in situ conditions for the tests and access to the stimulated regions by mineback which permits direct observation of results. The five tailored-pulse concepts tested involve: Case A - a decoupled explosive, Case B - a decoupled explosive with propellant booster, Case C - a small-diameter propellant charge with pressurized water pad, Case D - three successive shots of Case C, and Case E - a full-diameter charge of a progressively-burning propellant. Results show a large increase in formation permeability for Case E, modest increases for Cases B, C, and D and a decrease for Case A that appears due to the formation of a stress cage. A comparison of Case E results with previous tests suggests a multiple fracture criterion based on pressure rate with little effect of peak pressures.