Estimating Fracture Apertures from Hydraulic Data and Comparison with Theory

Abstract

Estimates of fracture openings, or apertures, were made fro massive hydraulic fracture experiments at the Hot Dry Rock geothermal reservoir at Fenton Hill, New Mexico. The basis of these estimates is that if the injection rate is suddenly increased during fracturing, and the subsequence pressure increase to sustain this additional flow is measure, then the pressure increase must be related to the fracture aperture. More detailed considerations indicate that the fracture aperture estimated in this manner is affected by the nature of the fracture geometry, its propagation distance, and its viscous characteristics, but these effects are surprisingly unimportant. The result is a reasonable accurate aperture estimate, which considering the elusive nature of this measurement by other means, is quite satisfactory. These estimates are in good agreement with the fracturing theory of Geertsma and de Klerk.