Fracture Characterization From Attenuation And Generation Of Tube Waves

Abstract

Results are presented from experiments carried out in conjunction with the USGS at the Hubbard Brook Experimental Forest near Mirror Lake, New Hampshire. The study focuses on our ability to obtain orientation and transmissivity estimates of naturally occuring fractures. The collected dataset includes a four-offset hydrophone vertical seismic profile, full waveform acoustic logs at 5, 15 and 35 kHz, borehole televiewer, temperature, resistivity, and SP logs, and well-to-well pu,mp test data. While the basic assumptions of the VSP generation model are found to be tenable, fracture aperture estimates from VSP were generally one order of magnitude lower than corresponding pump test or Stoneley wave attenuation results. A new model for tube wave generation which makes use of fracture stiffnes (stress/length) is presented.