NOMENCLATURE

Development of borehole geophysics has recently focused on reservoir characterization. Within this effort, extensive full waveform acoustic surveys have demonstrated a correlation between the occurance of open fractures and attenuation of Stoneley waves. A relationship is obtained here between fracture permeability and attenuation of Stoneley waves, on the basis of a physical mechanism. This mechanism involves an energy transfer under the form of a fluid flow inside permeable formations. It is applied to the cases of a single open fracture, a multi-fractured medium and a homogeneous porous medium. Theoretical results show the effects of frequency, borehole radius, permeability, fracture density and porosity on attenuation. The single fracture theory is applied to observed attenuation data due to isolated large open fractures: the theoretical fracture apertures obtained compare favorably to values determined from packer tests